Tax-loss harvesting and the wash-sale rule

There is a move that sounds, at first, like something only a cynic or a tax cheat would do: deliberately sell an investment while it's down, on purpose, to lose money. It feels wrong in the gut. We're trained from the first lesson of investing to buy and hold, to not panic-sell, to let things ride — and here is a technique that says, in certain moments, go ahead and sell the loser, lock in the loss, do it intentionally. The name for it is tax-loss harvesting, and it is one of the most genuinely useful, completely legitimate tools a taxable investor has. It is also wrapped in a rule — the wash-sale rule — that scares people away from it entirely, because they've heard that if you do it wrong you 'lose the deduction,' and nobody ever explained what that actually means. This lesson takes both apart, slowly, until the fear is gone and the move is something you could do this afternoon.

Three fears do almost all the work of keeping people away from this, so let's name them now and start taking the air out of each. The first: selling at a loss feels like locking in failure — like admitting the investment was a mistake and making the loss permanent. It isn't, and the reason is the whole trick: you don't leave the market. The instant you sell the loser, you buy something almost just like it, so your money stays invested and rides the recovery — you've only handed the paper loss to the IRS to lower your tax bill. The second fear: I'll trip the wash-sale rule and lose my deduction. The wash-sale rule is real, but it's one simple timing rule — don't rebuy the same thing within 30 days — and in almost every case breaking it doesn't destroy your loss at all; it just postpones it. There's exactly one version that's truly costly, and once you can see it, it's easy to avoid. The third, the quiet one: isn't this a shady loophole the IRS will come after me for? No. The rules that make tax-loss harvesting work are spelled out in plain language in IRS Publication 550. Most major robo-advisors do it automatically, every day. Every wealth manager does it for their clients. The wash-sale rule exists precisely because the IRS drew a clear line around what's allowed — and staying on the right side of a line the IRS itself drew is the opposite of cheating.

Your guide through most of this is Maya Chen — 24, a software engineer in Seattle earning $145,000 a year, in a state with no income tax. You've met her before, twice in ways that matter here. Back in Lesson 14 she opened a robo-advisor account, and one of the things the robo quietly does is tax-loss harvest for her automatically; she's seen the line on her dashboard — 'tax-loss harvesting: $380 banked this year' — and never really known what it meant. And in Lesson 25 she opened a second, self-directed taxable brokerage account, the kind where she chooses and buys the funds herself. So Maya is perfectly placed to learn this from both ends: first by looking over the robo's shoulder to see what 'harvesting $380' actually did, then by learning the rule behind it, and finally by doing it with her own hands in her self-directed account. We'll also spend real time with David and Sarah Okonkwo — the high-earning Houston couple from earlier lessons — because tax-loss harvesting pays off most at a high tax bracket, and theirs is where the dollars get large enough to see the whole machine clearly.

One orienting promise before we start, so you know the shape of what's coming. By the end you'll know exactly what harvesting a loss does (it offsets your gains, then up to $3,000 of your regular income, then carries forward for as long as you live); you'll know the wash-sale rule cold (the 61-day window, the 30-day clock, and the one account you must never rebuy in); you'll know the simple workaround that lets you harvest and stay invested at the same time; and you'll know the honest catch that the sales pitches leave out — that harvesting mostly defers tax rather than erasing it, so it's a real benefit but not free money. This lesson lives inside the taxable brokerage account from Lesson 25; it leans on the capital-gains basics from Lesson 38; and it points forward to where a few details get their full treatment — qualified dividends in Lesson 40, where each investment belongs in Lesson 41, the nuts and bolts of cost-basis tracking in Lesson 42, and reading the tax forms in Lesson 43. Let's begin where the fear is loudest: with the idea of losing on purpose.

This section does only two things, and both are about clearing the ground before we build on it. First it takes the three fears from the intro and sets each one down properly, because a fear you can see clearly is a fear you can manage. Then it gives you the one-sentence version of what tax-loss harvesting actually is, and the single most important boundary on it — that it only works in a taxable account — using the exact moment Maya first noticed it happening. After this, everything is detail.

§1.1 — The three fears, named and shrunk

Fear one: selling at a loss means locking in the loss and admitting failure. This is the emotional one, and it's worth meeting head-on because it's the reason most people never harvest a single loss. Here's the reframe. When an investment you own drops below what you paid for it, you already have the loss — it's sitting right there in your account as a lower balance, whether you do anything or not. That kind of loss, a drop you haven't sold, is called an unrealized loss: it's real on paper but invisible to the tax system, because the tax system only notices when you actually sell. Tax-loss harvesting is simply choosing to sell so the loss becomes real in the eyes of the IRS — a realized loss — and then immediately buying something nearly identical so your money stays in the market. You are not crystallizing a defeat and walking away poorer. You're converting a paper loss you already have into a tax deduction, while keeping your investment exposure almost exactly where it was. The market doesn't know you sold; your tax return does. That's the entire move, and it's the opposite of giving up.

Fear two: I'll trip the wash-sale rule and lose the deduction. People say this phrase — 'lose the deduction' — as if the loss vanishes in a puff of smoke, money set on fire. It almost never does. The wash-sale rule is one timing rule: if you sell at a loss and buy the same (or a nearly identical) investment back within 30 days, the IRS won't let you take that loss this year. But — and this is the part nobody mentions — in the ordinary case the disallowed loss isn't destroyed. It gets quietly attached to your replacement shares and you get it back later, when you eventually sell those. The wash-sale rule mostly delays a loss, it doesn't delete it. We'll prove this with real numbers in §3. There is one genuinely costly exception — rebuying inside an IRA — and we'll spotlight it so you can route around it. But the blanket fear, the sense that one wrong click incinerates your money, is simply not how the rule works.

Fear three: this is a loophole, and using it will get me audited. Set this one down completely. Tax-loss harvesting is not a gray-market hack — the rules that make it work are spelled out in IRS Publication 550, the IRS's own guide to investment income and expenses. The wash-sale rule itself, the thing people fear, is the IRS deliberately drawing the boundary of what's allowed; harvesting a loss and respecting that 30-day boundary is following the instructions, not evading them. This is so mainstream that it's automated: in Lesson 14 you saw that Maya's robo-advisor harvests her losses for her, on its own, scanning her account every single day. Wealth managers do it for their richest clients as a standard service. It is one of the most ordinary, well-trodden moves in all of personal taxation. The only people who should worry are the ones who try to be too clever about the 30-day rule — and by the end of this lesson, you'll know exactly where that line is.

§1.2 — What it actually is — and why it only works in a taxable account

Here is tax-loss harvesting in one sentence, the version to carry with you: you sell an investment that's worth less than you paid, which creates a capital loss the IRS will let you use to lower your taxes, and you immediately buy a similar investment so you stay invested — turning a temporary dip into a permanent tax benefit without leaving the market. A capital loss is just the mirror image of a capital gain from Lesson 38: a gain is selling for more than you paid, a loss is selling for less. And just as a realized gain triggers tax, a realized loss earns you a tax benefit. Harvesting is the deliberate act of realizing losses you happen to have, on your timing, to capture that benefit. Everything else in this lesson is about how that benefit works (§2), the one rule that governs the timing (§3), how to do it without leaving the market (§4), and whether it's even worth your while (§5).

Now the single most important boundary, the one that determines whether harvesting is even possible for a given dollar: it only works in a taxable brokerage account. Think back to the three kinds of account from Lesson 25. Inside a tax-advantaged account — a 401(k), a traditional or Roth IRA, an HSA — gains and losses are invisible to the IRS; you don't report them, you don't pay tax on gains there, and so you get no benefit from losses there either. There is simply nothing to harvest. Harvesting only means anything in the taxable account, the one where every gain and loss does show up on your tax return. So when the rest of this lesson talks about selling losers for the tax benefit, it is always, only, about your taxable brokerage account. The money in your retirement accounts plays by entirely different rules and sits this lesson out. (This will matter enormously in §3, where you'll learn that buying inside an IRA at the wrong moment can actually poison a loss you harvested in your taxable account — the IRA can't give you a benefit, but it can take one away.)

Which brings us back to Maya's dashboard. In Lesson 14 she set up a robo-advisor — a fictional one we've been calling Vista Invest — and funded an individual taxable account with it. Every quarter when she logs in, there's a small green line in the activity summary: 'Tax-loss harvesting: $380 banked this year.' For a couple of years she's glanced at it, vaguely pleased, with no idea what it meant. Was the robo making her $380? Losing her $380? Saving her $380 in taxes? She's about to find out it's none of those exactly — and that the real answer is more interesting and more honest than the dashboard's cheerful green number suggests. To understand what her robo did, we first have to understand what a harvested loss is actually worth. That's §2.

A harvested loss isn't valuable on its own — it's valuable because of the three jobs the tax code lets it do, in a fixed order. This section builds that up in three steps: first the physical mechanic of harvesting (sell, realize, replace, stay invested), then the three-tier payoff a loss unlocks (offset your gains, then your income, then carry the rest forward), and finally the part that decides how big the payoff is — which losses are worth the most, and why a high tax bracket like the Okonkwos' turns the same move into far more money. This is the section that answers 'what is a loss actually worth?'

§2.1 — The mechanic: sell the loser, keep the position

Start with the physical sequence of what happens, because once you see it as four small steps it stops being mysterious. Step one: you own a fund or stock in your taxable account that has dropped below what you paid for it — you have an unrealized loss. Step two: you sell it, which realizes the loss — now it's a real capital loss the IRS recognizes, recorded against the cost basis (what you originally paid, the term from Lesson 25) you had in those shares. Step three — and this is the step that makes the whole thing safe — you immediately take the cash from that sale and buy a replacement security: a different investment that's similar enough to keep your portfolio doing the same job, but not identical (the 'not identical' part is what §3 and §4 are all about). Step four: you keep that replacement, so your money never left the market. The diagram below walks this exact flow.

The reason step three matters so much is the thing people miss when they imagine harvesting as 'selling at the bottom.' If you sold your loser and sat in cash, you'd be exposed to exactly the risk every investor fears: the market rebounds the next week and you miss it, having sold low and bought nothing. Harvesting avoids that entirely. Because you buy the replacement the same day — often within the same minute — you're never out of the market; you simply swapped one near-equivalent holding for another and pocketed a tax loss in the process. If a total-market index fund is down, you sell it and buy a different total-market index fund (a different provider, a different underlying index) that will rise and fall almost in lockstep with the one you sold. Your exposure to stocks is unchanged. Your risk is unchanged. The only thing that changed is that you now have a realized capital loss to put to work — and a slightly lower cost basis in the new shares, which is the catch we'll come to in §4. For now, hold the picture: harvesting is a swap, not an exit.

§2.2 — What the loss buys you: gains, then $3,000, then forever

So you've realized a capital loss. What does the tax code actually let you do with it? Three things, and they happen in a strict order set by IRS rules — you don't get to choose the order, but knowing it tells you how much a loss is worth. The first job a loss does is offset your capital gains, dollar for dollar. If you sold something else this year at a $5,000 gain and harvested a $5,000 loss, they cancel — you owe no capital-gains tax on that $5,000, because for tax purposes you made nothing. One important wrinkle here, which we'll lean on in §2.3: losses first offset gains of the same type. Short-term losses (on things held a year or less) cancel short-term gains first; long-term losses (held more than a year) cancel long-term gains first; only after that does a leftover loss of one type cross over to cancel the other. The bookkeeping happens automatically on a form called Schedule D when you file — you don't do this math by hand — but the order is why the type of gain you're offsetting changes the value of the loss.

The second job is the one most people don't realize a loss can do, and it's quietly the most valuable per dollar: after your losses have wiped out all your capital gains, you can use up to $3,000 of leftover net loss to offset your ordinary income — your salary, your wages, the income taxed at your regular rate. That's right: a stock-market loss can lower the tax on your paycheck. The cap is $3,000 a year ($1,500 if you're married and file separately), and it's worth knowing that this $3,000 figure is fixed in the law and has not changed since 1978 — it isn't adjusted for inflation, so if it had kept pace it would be something like $13,000–$16,000 today. It's a small door, but a genuinely useful one, especially in a year when the market fell and you have no gains to offset. The third job catches everything left over: any net loss beyond the $3,000 you used this year carries forward to next year, and the year after, indefinitely — there is no expiration. It keeps its identity as it goes (a long-term carryover stays long-term), and you use it up $3,000 at a time against income, or all at once against a future gain, for as long as you live. (One sober footnote: a carryforward is personal — it generally can't be passed to your heirs, so an unused pile of losses is used on your final return and then ends. We'll touch the planning side of that in Lesson 61.)

Let's put real numbers on the cap and the carryforward, with Maya, in a rough market year. Suppose stocks fall hard — a 2022-style year — and across her taxable funds Maya harvests $10,000 of losses (selling the dips and rebuying replacements, so she stays invested the whole time). She has no capital gains that year to offset. So the order runs straight to the second and third jobs: $3,000 of the loss offsets her ordinary income this year, and because she's in the 24% federal tax bracket, that saves her $720 in tax (24% of $3,000). The remaining $7,000 doesn't disappear — it carries forward. Next year it knocks another $3,000 off her income (another $720 saved), the year after another $3,000 ($720), and in the fourth year the final $1,000 (saving $240). Over four years, that single $10,000 harvest reduces her taxable income by the full $10,000 and saves her about $2,400 in tax — drawn down $3,000 at a time because that's the annual gate. Same loss, parceled out across years, never wasted. That is the cap and the carryforward working exactly as designed.

§2.3 — Which losses are worth most — and why a high bracket changes everything

Not every harvested dollar is worth the same, and understanding why is what separates someone going through the motions from someone who knows what they're doing. The value of a harvested loss is whatever tax it saves you — and that depends entirely on the rate of the thing it's offsetting. Recall the two rate worlds from Lesson 38: long-term capital gains and qualified dividends are taxed gently, at 0%, 15%, or 20%; ordinary income and short-term gains are taxed at your full regular rate, which runs from 22% up to 37% for most working people. So a dollar of loss that erases a dollar of long-term gain saves you only the long-term rate (say 15%), while a dollar of loss that erases ordinary income — the $3,000 door — or that erases a short-term gain saves you your full ordinary rate (say 24% or 35%). The same loss is worth more when it's killing higher-taxed income. That's why the $3,000-against-income door is the sweetest one, and why offsetting a short-term gain is more valuable than offsetting a long-term one. You can't fully control which gains your losses land on — the same-type-first ordering decides that — but you can understand that a harvest in a year you have short-term gains, or a harvest that frees up the $3,000 income offset, is punching above its weight.

This is also exactly why tax-loss harvesting pays off most for high earners — and why the Okonkwos are the right household to watch the full machine on. David and Sarah, in Houston, have a combined income of $575,000 and a $545,000 taxable brokerage account alongside their retirement accounts. Their tax rates are near the top: their long-term gains and qualified dividends are taxed at 15% plus the 3.8% net investment income tax that high earners pay on investment income — 18.8% all in — and their ordinary income is taxed at 35%. Now suppose a sharp market drop leaves one of their international stock-fund lots, bought near a peak, sitting on a $30,000 loss. David harvests it: he sells the lot (realizing the $30,000 loss) and immediately buys a different international index fund to stay invested. That same year, rebalancing and fund distributions left them with $18,000 of realized long-term capital gains. Watch the loss go to work in order.

First, the $30,000 loss cancels all $18,000 of their long-term gains — gains they would otherwise have paid 18.8% on — saving them $3,384 (18.8% of $18,000). Next, $3,000 of the leftover loss offsets their ordinary income at their 35% rate, saving another $1,050. That's $4,434 of tax cut in a single year from one harvest. And the remaining $9,000 of loss carries forward, a stockpile ready to cancel future gains or chip at income for years to come. Notice the gap between Maya and the Okonkwos: the very same act — harvest a loss, offset a gain, take the $3,000 — saved Maya $720 and saved the Okonkwos $4,434, because their rates are so much higher. (And it could be larger still: if those $18,000 of gains had been short-term, they'd face the Okonkwos' full 38.8% rate — their 35% ordinary rate plus the same 3.8% surtax that hits all their investment income — instead of 18.8%, so cancelling them would have saved $6,984. The higher the rate of what you erase, the more the loss is worth.) Harvesting isn't equally useful to everyone — it scales with your tax bracket, which is the first clue to the 'should you bother?' question we'll settle in §5. But first, the rule that governs every one of these moves: the wash-sale rule.

This is the rule everyone has half-heard and almost nobody can state correctly, and it's the heart of the lesson — so it gets the most room, in three parts. First, the rule itself and the 61-day window it creates, with a picture that makes the timing click. Then the reassuring truth that breaking it in the ordinary way only defers your loss rather than destroying it — proven with numbers. And finally the one version that genuinely is destructive, the IRA trap, plus all the quiet ways the rule reaches across your accounts and your spouse's that catch careful people off guard. By the end the wash-sale rule should feel like what it is: a single timing constraint, easy to respect once you can see it.

§3.1 — The rule, and the 61-day window

Here is the wash-sale rule in plain language, straight from IRS Publication 550 and the law behind it (Internal Revenue Code §1091): if you sell a security at a loss and buy the same or a substantially identical security within 30 days before or 30 days after that sale, the IRS disallows the loss for this year. The phrase to underline is 'within 30 days before or after.' Most people picture only a forward window — don't rebuy for 30 days after selling. But the rule also looks backward: if you bought more shares in the 30 days leading up to your loss sale, that purchase can trigger it too. Put the two halves together with the day of the sale itself and you get a 61-day danger zone: 30 days before, the sale day, and 30 days after. The practical takeaway is a single number — to be completely safe rebuying the identical thing, wait until the 31st day after you sell. And these are calendar days, not trading days; weekends and holidays count, so don't try to game the count around them.

The other phrase that matters is 'substantially identical,' and it's deliberately fuzzy — we'll spend §4.1 on exactly how fuzzy. For now hold the clear cases: selling a fund and rebuying the very same fund is obviously substantially identical and triggers the rule; selling one fund and buying a genuinely different one (a different index, a different company) generally does not. The rule is also triggered by more than a plain purchase — buying through an option or a contract to acquire the security counts too — and, crucially, it applies only to losses. You can never have a wash sale on a gain; selling something for a profit and rebuying it immediately is perfectly fine. The wash-sale rule exists for one reason: to stop people from claiming a tax loss while never actually giving up their position — selling at 4:00 and rebuying the identical thing at 4:01 purely to manufacture a deduction. That's the abuse it blocks. The diagram below shows the 61-day window two ways: a harvest that trips the rule, and a clean harvest that respects it.

Read the two timelines together and the rule stops being abstract. In the top timeline, the investor sells at a loss on day 0 and rebuys the identical fund on day 10 — squarely inside the 61-day window — so the loss is disallowed for the year. In the bottom timeline, the investor does one of the two things that keep a harvest clean: either they wait until day 31 to rebuy the identical fund, or (far more common, and the subject of §4) they rebuy a similar-but-not-identical fund immediately, which isn't 'substantially identical,' so the clock never starts. Same goal, same staying-invested, but the second path banks the loss this year. That's the entire skill of harvesting: realize the loss, and don't reacquire the identical security inside the window. Everything else is detail.

§3.2 — Disallowed isn't destroyed: the loss is only deferred

Now the reassurance that defuses the second great fear, and it's worth slowing down for because it's the single most misunderstood fact about the wash-sale rule. When a normal wash sale disallows your loss, the loss is not gone. The IRS takes the disallowed loss and adds it to the cost basis of your replacement shares — it rolls into what you're treated as having paid for the new shares. A higher basis means a smaller taxable gain (or a bigger loss) when you eventually sell those replacement shares, which is exactly the deduction you were denied, handed back to you later. On top of that, the holding period of the shares you sold carries over to the replacement — so you don't lose your progress toward the lower long-term rate either. The wash-sale rule, in the ordinary case, is a deferral, not a confiscation. It says 'not this year,' not 'never.'

Let's prove it with a clean example of its own (separate from the flow diagram above). Say you bought 100 shares of a fund at $55, a $5,500 cost basis. The price falls to $40, and you sell all 100 for $4,000 — a realized loss of $1,500. Then, eight days later (inside the window), you can't help yourself and rebuy 100 shares of the identical fund at $41, paying $4,100. That's a wash sale: your $1,500 loss is disallowed for this year. But here's what happens to it — the $1,500 is added to your $4,100 purchase, so your basis in the new shares isn't $4,100, it's $5,600 ($56 a share). Now fast-forward: the fund recovers and you sell those 100 shares at $60, for $6,000. Your taxable gain is $6,000 minus your $5,600 basis — just $400. Compare that to the world where the rule didn't exist: you'd have taken the $1,500 loss up front, kept a $4,100 basis, and later owed tax on a $1,900 gain — which, netted against the $1,500 loss you took earlier, is the same $400 of net taxable income. Identical outcome. The wash sale didn't cost you the $1,500; it just moved when you got to use it. This is why a wash sale is, most of the time, an annoyance rather than a disaster — and why the people who panic about it are usually panicking about nothing.

§3.3 — The IRA trap, and the reach you don't see

Now the exception — the one version of a wash sale that really does destroy the loss for good, permanently, with no later payback. It happens when the replacement shares are bought inside an IRA (traditional or Roth). The IRS settled this in a 2008 ruling (Revenue Ruling 2008-5): if you sell a security at a loss in your taxable account and buy the substantially identical security in your IRA within the window, the loss is disallowed exactly as before — but because an IRA has no taxable cost basis to adjust, the disallowed loss has nowhere to go. The deferral mechanism from §3.2 simply doesn't exist inside an IRA. So the loss isn't postponed; it's gone, forever. This is the worst outcome in the entire lesson, and it's the reason the boundary from §1.2 cuts both ways: an IRA can never give you a harvesting benefit, but it absolutely can take one away. The clean rule: when you've harvested a loss in your taxable account, do not buy that security — or anything substantially identical — in any of your IRAs for 30 days. For the Okonkwos this is not hypothetical; they hold $245,000 across traditional IRAs, and if David harvested that international-fund loss in the taxable account and an automatic investment dropped the same fund into his IRA a week later, that $30,000 loss — worth $4,434 to them this year — could vanish entirely.

That example points at the rule's most underestimated feature: it reaches across all of your accounts, and even into your spouse's. The wash-sale rule doesn't care which account does the buying. A purchase in your taxable account at a different brokerage, a purchase in your IRA, a purchase in your spouse's account, even a purchase by a corporation you control — any of them, of the substantially identical security inside the window, can trigger the rule. (Pub 550 says this directly: if you sell at a loss and your spouse or a company you control buys substantially identical stock, you have a wash sale — even if you file separate returns.) Two everyday habits are the quiet culprits here. The first is automatic dividend reinvestment — a DRIP — which keeps buying small amounts of your funds on a schedule; if a dividend reinvests into the fund you just harvested, it can trip the rule on a sliver of your loss. The second is automatic recurring investing, the very 'set it and forget it' habit we've praised all course long; if your monthly auto-buy lands on the harvested fund inside the window, same problem. Neither is a reason to stop automating — it's a reason to pause the reinvestment or the auto-buy on a fund the month you harvest it.

One last practical point, because it surprises people at tax time. Your broker tracks wash sales for you — but only within a single account, and only for the exact same security (the same fund, identified by its CUSIP number). When a wash sale happens inside one account, the broker flags it on your year-end Form 1099-B with a small code — 'W' — and adjusts the disallowed amount automatically. What the broker cannot see is a wash sale you created across accounts: a loss in your taxable account paired with a buy in your IRA, or at a different brokerage, or in your spouse's account. Those are invisible to any single broker's reporting, and tracking them is legally your responsibility. We'll read the actual 1099-B and that 'W' code in full in Lesson 43; the point to carry now is simply that the broker's automatic tracking has a hard edge, and the most dangerous wash sales — the IRA trap especially — live exactly in the blind spot beyond it. Which is the whole reason the smart way to harvest is to never create the conflict in the first place. That's §4.

Knowing the rule is half of it; the other half is the handful of moves that let you harvest cleanly and the honesty about what you're really getting. This section has four parts. First, the workaround that makes harvesting practical — buying a similar-but-not-identical fund so you never trigger the clock — and the genuine gray area inside it. Then the catch the sales pitches skip: harvesting mostly defers tax rather than erasing it, so it's a real benefit but not free money. Then a fair look at what your robo-advisor is actually doing when it harvests, and what that's honestly worth. And finally the one asset class the wash-sale rule currently doesn't touch at all — cryptocurrency — and the fast-moving law around it.

§4.1 — The workaround, and the 'substantially identical' gray area

The whole practical art of harvesting is this: sell the loser and immediately buy something similar enough to keep your portfolio doing the same job, but different enough that it isn't 'substantially identical.' Do that, and the wash-sale clock never starts — you bank the loss this year and you never leave the market. The standard move with index funds is to swap between two broad funds that track different underlying indexes. Sell a total-stock-market fund built on one index and buy a total-stock-market fund built on a different index from a different provider; the two will rise and fall almost identically, so your exposure is unchanged, but because they follow different indexes they're treated as different securities. The Bogleheads community keeps informal lists of these 'tax-loss-harvesting partners' for exactly this purpose. The cleanest, safest version is always: different index. That's the move that's beyond dispute.

Now the honest gray area, because pretending it's settled would be a disservice. The IRS has never actually defined 'substantially identical' for mutual funds and ETFs. Publication 550 spells it out for stocks and bonds of a company, but it is simply silent on fund-to-fund swaps — there's no regulation, no ruling, no court case drawing the line. That leaves three zones. Clearly safe: two funds tracking different indexes (a total-market fund versus an S&P 500 fund, or two total-market funds built on different index providers). Clearly not safe: two share classes of the very same fund, or a mutual fund and its own ETF version — those are the identical fund in different wrappers, and swapping them is a textbook wash sale. And then the genuinely contested middle: two different funds from different companies that track the exact same index — say, two different S&P 500 funds. One camp (the careful one, including the planner Michael Kitces) argues that funds tracking the identical index, holding virtually the identical stocks, are arguably substantially identical and a wash-sale risk. The other camp notes that they're legally distinct securities from different issuers and the IRS has never said otherwise, so in practice it's widely done. There's no certain answer, and an honest lesson won't pretend there is. The conservative path threads it neatly: stick to different indexes and the question never comes up. And if you ever want zero ambiguity — for instance with a single stock, where no 'similar but different' substitute really exists, since a competitor is a different company with different risks, not a stand-in — the bulletproof move is the old-fashioned one: sell, wait the full 31 days, and rebuy, accepting that you're out of that specific position for a month.

§4.2 — The honest catch: deferral, not free money

Here is the part the cheerful green dashboard number and the advisor's sales pitch tend to leave out, and it's the most important idea in the lesson for keeping your expectations honest. When you harvest a loss and buy a replacement, your cost basis in that replacement is lower — it's whatever you just paid, which (after a drop) is less than your original purchase. A lower basis means that when you eventually sell the replacement, your taxable gain will be bigger by exactly the amount of the loss you harvested. So the tax benefit you took today comes with a matching larger tax bill tomorrow. Tax-loss harvesting, in its purest form, doesn't erase tax — it defers it, moving the bill from the future into a deduction today. As the Bogleheads wiki puts it bluntly, it's more a tax-deferral strategy than a tax-reduction one. This is not a reason to skip it; deferral is genuinely valuable. It's a reason to understand what you actually have, so you neither overvalue it nor get blindsided later.

So if it's mostly deferral, where does the real, permanent benefit come from? Three places. First, the time value of money: a tax dollar you don't pay until years from now is cheaper than one you pay today, because you get to invest it in the meantime — deferral alone is worth something. Second, and most concretely, rate arbitrage: that $3,000-against-ordinary-income door deducts at your high ordinary rate now, while the larger gain it creates later is usually taxed at the lower long-term rate — you're swapping a high-rate deduction for a low-rate future gain, which is a true, permanent saving, not just timing. Third, the endgames where the deferred gain is never taxed at all: if you eventually sell in a year your income is low enough to land in the 0% long-term bracket, or if you simply hold the replacement until you die, when the basis resets to market value for your heirs (the step-up from Lesson 25, taught in full in Lesson 61) — in both cases the deferred gain quietly evaporates and the deferral becomes outright elimination.

Put numbers on it with Maya's robo $380, and the honest picture finally comes into focus. That $380 of harvested losses, used against her ordinary income at her 24% rate, saves her about $91 in tax this year (24% of $380). But because the robo rebought replacements at a lower basis, her future gain is $380 larger, and when she eventually sells she'll owe the 15% long-term rate on that extra $380 — about $57. So the real, permanent benefit isn't the $91, and it certainly isn't the $380 the dashboard cheerfully 'banked' — it's roughly the difference, about $34 (the 9-point gap between her 24% deduction now and her 15% gain later), plus the time value of having deferred that $57 for years, plus the chance the $57 never comes due at all if she's in a low bracket someday or holds to the end. The dashboard's green '$380 banked' is the harvested loss, not the money saved; the money saved is more like $34 of certain benefit and a deferral worth a bit more. That's still real, and it's free in the sense that the robot did it while she slept — but it is emphatically not $380 in her pocket. Which leads to the oldest and best advice in this whole area: don't let the tax tail wag the dog. Never distort a sound investment plan — never sell something you shouldn't, or hold something you shouldn't, or take on tracking risk you don't want — just to chase a harvest. The tax benefit is a nice bonus on top of good investing; it is never a reason to invest badly. (And in the rare case where harvesting would offset a gain you'd have paid 0% on anyway, it can even be a small net negative — another reason it's a tool, not a reflex.)

§4.3 — What the robot is actually doing — and what it's worth

Now we can finally answer Maya's question from §1 — what did her robo actually do to 'bank $380'? — and judge robo tax-loss harvesting fairly, neither dismissing it nor swallowing the marketing. The mechanics first. A robo-advisor's real advantage over a human doing this by hand is cadence: it scans your taxable account every single trading day, so it catches brief dips that a once-a-year harvester would sleep through. When a holding drops below its basis by a set threshold, the software sells it and, in the same motion, buys a pre-chosen alternate fund that tracks a different index — exactly the §4.1 workaround, automated — so you stay invested and never trip the wash-sale rule. The better robos go further to avoid the traps from §3: they coordinate across your linked accounts (some, like Betterment, keep a primary, secondary, and even tertiary fund per asset class specifically so a deposit into your IRA can't create the permanent IRA-trap loss), and they manage dividend reinvestment so a DRIP doesn't trip the clock. The log below is what stood behind Maya's '$380' — the actual harvest events her robo executed.

Now the fair judgment, because robos advertise tax-loss harvesting as 'tax alpha' — extra return from tax savings — and the number is routinely overstated. The honest research lands far below the marketing. A widely cited 2020 study in the Financial Analysts Journal found a tax-loss-harvesting benefit of roughly 1% a year in an idealized form, falling to about 0.82% a year once the wash-sale rule was properly enforced — and it varied enormously with the era, the investor's tax rates, and how volatile markets were. Vanguard's own 2024 analysis put the realistic range around 0.5% to 1.3% a year, with a typical figure near 1% and — importantly — close to zero for an investor already in the 0% capital-gains bracket. The fair summary: real, modest, and highly dependent on your situation, somewhere in the neighborhood of a few tenths of a percent to about 1% a year for someone in a high bracket with a volatile, sizable taxable account — and remember from §4.2 that even that is mostly deferral, not pure savings. The robo earns its keep here by doing something tedious, daily, and wash-sale-aware that you'd probably never do by hand — but the benefit is a quiet tailwind, not the windfall the word 'alpha' implies. One cautionary note, picked up properly in the Scam Radar below: even a legitimate, well-known robo can get this wrong. In 2018 the SEC penalized Wealthfront $250,000 after finding that, despite telling clients it monitored their accounts to avoid wash sales, it failed to do so — wash sales occurred in about 31% of the accounts enrolled in its harvesting program over a three-year stretch. The technique is sound; the execution still has to be checked.

§4.4 — The one asset the rule doesn't touch (for now): crypto

There's a striking gap in the wash-sale rule that you should understand precisely, because it's both genuinely useful and genuinely unsettled. As of this writing — tax year 2026 — the wash-sale rule does not apply to directly held cryptocurrency. The reason is structural: the law (§1091) disallows losses only on 'stock or securities,' and the IRS classifies cryptocurrency as property, not a security (a treatment dating to its 2014 guidance, Notice 2014-21). Crypto simply falls outside the rule. The practical consequence is that a crypto investor can sell a coin at a loss to harvest it and rebuy the very same coin immediately — no 30-day wait, no substantially-identical worry — and still claim the loss. It's the one corner of harvesting where you can have your loss and your identical position at the same instant.

But state the status carefully, because this is exactly the kind of thing that changes. Congress has tried to close this gap repeatedly and, so far, failed: a 2021 bill (the Build Back Better Act) would have extended the wash-sale rule to digital assets but died in the Senate; the major 2025 tax law (the reconciliation act signed that July) dropped a crypto-tax amendment before passage; and as of mid-2026 a fresh bipartisan bill — the Digital Asset PARITY Act — has been introduced in the House and would apply the wash-sale rule to crypto, but it has not passed and is not law. So the accurate statement is: today, no enacted federal law applies the wash-sale rule to spot crypto, but several proposals are live and the rule could change, possibly with little warning. Three cautions belong with that. First, the law is fast-moving — verify the current status before relying on it. Second, even without a wash-sale rule, the IRS could in principle challenge a purely cosmetic sell-and-instantly-rebuy under broader anti-abuse doctrines, and new crypto tax-reporting forms now make such activity far more visible. Third — a common confusion — this carve-out is only for crypto held directly; if you hold crypto exposure through securities, like a crypto stock (a company such as a crypto exchange) or certain crypto futures funds, those are securities and the wash-sale rule applies to them normally. The direct-crypto gap is real today, but treat it as a ledge that may not be there next year.

We've built the whole machine; the last question is the practical one: is it worth running for you? Tax-loss harvesting is a tool, not a duty, and for a lot of people the honest answer is 'barely, or not yet.' This closes the lesson in two parts — a clear-eyed list of when harvesting earns its effort and when to skip it, and then a quick which-one-is-you across the cast, so you can find the situation nearest your own and know exactly what to do with it.

§5.1 — When it's worth it, when to skip it

Start with the gates, because if you fail the first one, nothing else matters. Harvesting is only possible in a taxable brokerage account — if all your investing is inside a 401(k), IRA, or HSA, there is literally nothing to harvest, and you can close this lesson with a clear conscience. Past that gate, the benefit scales with three things. It scales with your tax bracket: the same harvest that saved Maya $720 saved the Okonkwos $4,434, so the higher your rate, the more worth your while it is — and for someone in the 0% long-term bracket, harvesting against gains can be worth nothing at all, or even slightly negative. It scales with how much real loss you have to work with: a market that's down, a volatile holding, a lot bought near a peak — these are the raw material, which is why down years (2022, the March 2020 crash) are harvest season and a smoothly rising market offers little. And it scales with whether you have gains to offset, though even with no gains the $3,000-against-income door makes a harvest worth doing in a down year.

Then the frictions and the timing rules that decide the edges. There's a real deadline: a loss counts for a tax year only if you sell by the last trading day of that year (the loss is fixed on the trade date), so harvesting is a December chore, not a 'I'll get to it in the spring' one — and beware harvesting in late December and then rebuying in early January, which can throw the loss into the next year by tripping the window across the New Year. Small balances rarely justify the effort: the bid-ask spread and the bookkeeping can eat a tiny harvest, and a few dollars of benefit isn't worth distorting your portfolio for. If you already carry a large loss carryforward — say you harvested heavily in a crash and now have $40,000 banked, usable at only $3,000 a year against income absent gains — there's little point harvesting still more; you already have years of deductions queued. Two quieter upsides are worth knowing: lowering your income with the $3,000 offset, or cancelling gains, also lowers your adjusted gross income (AGI) — the income figure your tax return is built on — which can ripple helpfully into things like Medicare premium surcharges or ACA health-subsidy thresholds down the line. And one fairness-and-accuracy caveat this no-state-tax cast can hide: states don't all follow the federal rules — a few (Pennsylvania and New Jersey, for instance) don't let you offset ordinary income or carry losses forward the way the IRS does — so if you live in a state with an income tax, check how it treats capital losses before counting on the full benefit (state income taxes get their own treatment in Lesson 46). None of this is complicated; it just rewards a little care. And above all, the §4.2 rule stands over all of it: don't let the tax tail wag the dog. A harvest is a bonus on good investing, never a reason to trade when you otherwise wouldn't.

§5.2 — Which one is you — and where Phase 6 goes next

Maya — let the robot do it, and learn to do the $3,000 yourself. For most of her money, Maya doesn't need to lift a finger: her robo-advisor harvests automatically, every day, wash-sale-aware, for the 0.25% she already pays it — and she now knows that the '$380 banked' on her dashboard is a real but modest benefit (worth perhaps $34 of certain savings plus some deferral), not $380 in her pocket. In her self-directed account from Lesson 25, the move she should actually learn is the simplest one: in a down year, sell a loser, buy a different-index replacement the same day, and take the $3,000 against her income — about $720 saved at her bracket, with the rest carried forward. That's 90% of the value for 10% of the complexity. Her lesson: harvesting is worth knowing, mostly easy, and not worth obsessing over.

The Okonkwos — harvest deliberately, because at their bracket the dollars are real. With a $545,000 taxable account and rates at 35% on income and 18.8% on gains, the Okonkwos are the household for whom manual, deliberate harvesting most clearly pays — a single down-year harvest saved them $4,434, and a large carryforward can shelter gains for years. Their two watch-outs are exactly the lesson's two traps: never let an automatic purchase rebuy a harvested fund inside their $245,000 of IRAs (the permanent IRA trap), and judge any advisor's '1% to manage and harvest your account' offer against what it's really worth — 1% of their taxable account is $5,450 a year, far more than the harvesting itself is likely to add, which is the Advisor's-Move question below. Their lesson: at a high bracket, harvesting is genuinely valuable and worth doing carefully — but worth far less than a 1% fee charged in its name.

And the household that should mostly skip it: anyone whose investing is entirely inside tax-advantaged accounts, or whose income lands them in the 0% capital-gains bracket. If you have no taxable account, there's nothing to harvest. If your long-term gains are taxed at 0% anyway, a harvested loss may save you nothing and could even cost you a future deduction. For a great many ordinary investors still filling their 401(k) and IRA, tax-loss harvesting is simply not yet relevant — and knowing that it doesn't apply to you is its own kind of useful. Wherever you land, the through-line holds: harvesting turns a paper loss into a real, legitimate, IRS-blessed tax benefit while you stay invested; the wash-sale rule is one timing line to respect, harmless if you do; and the whole thing is a modest, deferral-flavored bonus, never the point of investing. Next, in Lesson 40, we stay in the same taxable account and turn to the income side of it — dividends, and the surprisingly large difference between the 'qualified' kind taxed gently and the 'ordinary' kind taxed at your full rate — the very distinction that, as you've seen here, decides how much a harvested loss is worth.

Tax-loss harvesting is legitimate — which is exactly why its name gets borrowed to sell things that aren't. Because the technique sounds sophisticated and most people don't understand it, it's perfect cover for an overpriced service or an outright fraud. Here's what to watch for, and how to check and report it — and none of it is your fault to spot alone.

The overstated 'tax alpha' and the fee that eats it

The most common move isn't a scam so much as a sales exaggeration: an advisor or platform pitches tax-loss harvesting as a headline reason to hand over your money, implying it'll add 1%, 2%, even more to your return every year. You now know the honest range — a few tenths of a percent up to about 1% a year for a high-bracket investor with a volatile, sizable taxable account, and mostly deferral rather than permanent savings at that. When the pitched 'tax alpha' is suspiciously round and large, or quoted as a guarantee, that's the tell. Worse is when the harvesting is the justification for a 1%-of-assets annual fee: for the Okonkwos, 1% on their $545,000 taxable account is $5,450 a year — likely more than the harvesting itself will ever add. Paying a 1% fee to capture a benefit a 0.25% robo or a few minutes of your own time would capture is the expensive trap, not a service worth celebrating.

The cold 'tax-loss' approach and the fake platform

The outright fraud versions ride the same vocabulary. A stranger messages you — or a slick ad targets you near year-end, when taxes are on everyone's mind — offering to 'harvest your losses' or run a 'tax-optimized' strategy through a platform you've never heard of, often paired with crypto (where, as §4.4 noted, the loss-harvesting angle is real and therefore believable). The pattern is the usual one: urgency tied to a tax deadline, promises of guaranteed savings, and a push to move your money onto an unfamiliar app or to give a stranger trading access to your account. A real professional doesn't cold-message you a tax strategy, and a real tax benefit never requires moving your money somewhere you can't easily get it back.

Before you trust anyone with this, verify them — it's free and takes minutes. Check any advisor or firm in FINRA's BrokerCheck (brokercheck.finra.org) and the SEC's adviser tools at Investor.gov and adviserinfo.sec.gov, and read the disclosure section, which lists regulatory actions and complaints — the part that actually tells you something. (Remember the §4.3 Wealthfront case: even a registered, legitimate firm was penalized for botching wash-sale monitoring, so 'registered' means 'check the record,' not 'no need to look.') If a platform or 'advisor' can't be found in those databases at all, that absence is your answer.

And know where to report it, because reporting protects the next person even when it can't undo your own loss. Investment fraud or an unregistered seller: the SEC at Investor.gov (and its tip line, the TCR). A bad broker or registered rep: FINRA. Any fraud at all, even a near-miss where you lost nothing: the FTC at ReportFraud.ftc.gov. Online financial crime or account theft: the FBI's IC3 at ic3.gov. You won't be judged for reporting — the shame belongs to the person who ran the pitch, and reporting is how the next person is spared it.

If reading this set off a quiet alarm — because you once sold something at a loss and rebought it too soon, or you've never harvested a loss in your life and now feel like you've left money lying around for years — set the self-blame down. These are among the most common, most forgivable stumbles in all of investing, and in almost every version the fix is small and entirely ahead of you.

If you rebought too soon and tripped a wash sale, the most important thing to know is the §3.2 truth: in the ordinary case, you did not lose anything. The disallowed loss was added to the cost basis of your replacement shares, and you'll get it back as a smaller gain (or larger loss) when you eventually sell them — your broker even tracked it for you with that 'W' on your 1099-B and adjusted it automatically. It was a deferral, not a loss. The one version that genuinely costs you is the IRA trap from §3.3 — if the rebuy happened inside your IRA, that specific loss is gone for good. Even then, there's nothing to unwind and no penalty; you simply know now to never rebuy a harvested security inside a retirement account, and to pause your dividend reinvestment and auto-investing on a fund the month you harvest it. The mistake taught you the rule. That's a fair trade.

If you've never harvested at all, you have lost far less than it feels like — and possibly nothing. Remember the honest math from §4.2: harvesting is mostly deferral, and its real benefit is modest — Maya's whole year of robo-harvesting was worth perhaps $34 of certain savings. Years of not harvesting a small taxable account add up to a small number, not a fortune. You can't reach back and harvest losses from past years (a loss only counts in the year you actually sold). But going forward, the move is simple and available the moment the market next dips: sell a loser in your taxable account, buy a different-index replacement the same day, and take the deduction. If even that feels like too much to track, a robo-advisor will do it for you automatically for about 0.25% a year. Either way, the door is open from here on, and what you didn't capture before was never the windfall the brochures imply.

And if your worry is the opposite — that a surprise 'wash sale disallowed' line showed up on your 1099-B and you don't understand it — take a breath. That code 'W' just means your broker spotted a rebuy inside the window in that account and deferred a sliver of your loss onto your remaining shares; it's automatic, it's usually small, and it's not a flag that you did something wrong. The full read of that form, and that code, is Lesson 43. For now: it's a deferral, your software handles it, and it's not a problem you need to solve tonight.

The move

It's a polished, appealing pitch, usually delivered to someone with a sizable taxable account: "One of the ways we add value is tax-loss harvesting. We watch your account all year and capture losses to lower your tax bill — it's a benefit you'd never get managing this yourself, and it helps pay for our fee." For a household like the Okonkwos, with $545,000 in a taxable account and a high tax rate, it sounds not just plausible but smart. Here's what's underneath it.

The logic, and what it's really worth

The technique is real and, at a high bracket, genuinely worth something — you've seen it save the Okonkwos $4,434 in a down year. But two honest facts shrink the pitch. First, most of harvesting's value is deferral, not permanent savings (§4.2), and the realistic permanent benefit is modest — a few tenths of a percent up to roughly 1% a year for exactly this kind of account, per the independent research, not the larger numbers often implied. Second, and decisively: this is the single most automatable task in investing. The 'we watch your account all year' that the advisor charges for is precisely what a robo-advisor does for 0.25%, and what you can do yourself in a down year in about ten minutes. The question is never whether harvesting has value — it does — but whether it justifies the price being charged for it.

The DIY substitute

Harvesting yourself is genuinely simple: in a down year, sell a losing fund in your taxable account and buy a different-index replacement the same day, then let your tax software apply the loss. If you'd rather it be automatic and wash-sale-aware, a robo-advisor (Lesson 14) does daily harvesting for about 0.25% a year — a quarter of a typical 1% advisor fee. The legitimate version of the advisor's offer is a fee-only fiduciary charging a flat or hourly fee for real, coordinated tax planning — handling your IRA-trap exposure across accounts, the year-end timing, the asset-location decisions of Lesson 41. The version to question is the one whose whole compensation is 1% of your balance, justified largely by a service a robot does for a quarter of the price.

The tell — is your advisor worth the fee?

Three questions cut to it. First: "What is your total annual fee in actual dollars on my balance — and how much do you estimate the harvesting itself adds?" For the Okonkwos, 1% on $545,000 is $5,450 a year; if the honest harvesting benefit is a few hundred to maybe a couple thousand dollars and mostly deferral, the fee may dwarf the thing it's selling. Second: "How do you coordinate my harvesting across all my accounts, including my IRAs, to avoid a permanent wash-sale loss?" — a real tax manager has a crisp answer about the IRA trap and linked-account monitoring; a salesperson gets vague. Third: "What are you doing beyond harvesting that a 0.25% robo isn't?" — there are good answers (complex multi-account coordination, estate and asset-location planning, talking you out of panic-selling in a crash), and if the advisor has one, the fee may be earned. If the answer is essentially 'we harvest your losses,' you're paying 1% for something that's worth a fraction of it and that a robot does in your sleep.

If this lesson left you tense — that you'll trip a rule, or that you've been doing this wrong, or that 'losing on purpose' is somehow dangerous — let's set that weight down, because the real picture is far gentler than the jargon suggests.

The wash-sale rule, the part that scares people most, is one timing rule: don't rebuy the identical thing within 30 days. Break it the ordinary way and you haven't lost your deduction — it's deferred onto your replacement shares and comes back to you later, as we proved with real numbers in §3.2. There is exactly one genuinely costly version, rebuying inside an IRA, and now that you can see it, you can route around it with a single habit: don't buy a harvested fund in your retirement accounts for a month, and pause your auto-reinvestments on it. That's the whole defense. A rule you can state in one sentence and avoid with one habit is not something to be afraid of.

And if you're worried you've missed out by never harvesting, remember the honest scale of the thing. Harvesting is a modest, mostly-deferral benefit — real, worth doing when it's easy, but never the windfall the sales pitches imply. Maya's entire year of automatic harvesting was worth perhaps $34 of certain savings. You haven't forfeited a fortune; you've skipped a small bonus, and it's available to you from the next market dip onward. There's no version of this where the past needs unwinding — a loss only ever counts in the year you sell, so there's nothing to claw back and nothing to regret.

Most of all, hold onto the framing that started the lesson: this is not a loophole, and you are not getting away with something. Tax-loss harvesting is in the IRS's own publications; the wash-sale rule is the IRS itself drawing the boundary of what's allowed; every robo and every wealth manager does this as routine. Staying on the right side of a line the IRS drew is simply following the rules. Do the easy version — harvest a loser in a down year, buy a different-index replacement the same day, take your deduction, don't touch it in your IRA — and you've captured nearly all the benefit with none of the risk. The hard part was understanding it, and you've just done that.

Isn't selling at a loss just locking in the loss and admitting I was wrong?

No — and this is the misunderstanding that keeps most people from ever harvesting. The key is that you don't leave the market. The instant you sell the losing fund, you buy a similar one (a different index, so it isn't 'substantially identical'), so your money stays invested and rides any recovery. You've only converted a paper loss you already had — an unrealized loss, which exists whether you act or not — into a realized loss the IRS will let you use to lower your taxes. The market doesn't know you sold; only your tax return does. You're not crystallizing a defeat and walking away poorer; you're harvesting a tax benefit while keeping your investment exposure essentially unchanged. That's the opposite of giving up.

What exactly is the wash-sale rule, and how long do I have to wait?

The wash-sale rule (IRS Publication 550; Internal Revenue Code §1091) says that if you sell a security at a loss and buy the same or a substantially identical security within 30 days before or 30 days after the sale, the IRS won't let you deduct that loss this year. Counting the 30 days before, the sale day, and the 30 days after, that's a 61-day danger window — and these are calendar days, not trading days. The simple safe number to remember: if you're going to rebuy the identical thing, wait until the 31st day after you sell. The far easier path, and the one most harvesters actually use, is to not rebuy the identical thing at all — buy a similar fund tracking a different index immediately, which isn't 'substantially identical,' so the clock never even starts and you stay fully invested.

If I accidentally rebuy too soon, do I lose the loss forever?

Almost never. In the ordinary case, a wash sale only DEFERS your loss — it doesn't destroy it. The IRS adds the disallowed loss to the cost basis of your replacement shares, so you recover it as a smaller taxable gain (or a larger loss) when you eventually sell those shares; the holding period carries over too. Concretely: sell 100 shares at a $1,500 loss, rebuy within the window, and that $1,500 gets added to your new shares' basis — when you later sell them, your taxable gain is $1,500 smaller, which is exactly the deduction you were denied, handed back. There is one genuinely costly exception: if you rebuy the substantially identical security inside an IRA (the 'IRA trap,' Revenue Ruling 2008-5), the loss is permanently disallowed, because an IRA has no taxable basis to adjust. So the rule of thumb is: a wash sale in your taxable account is a deferral and rarely a big deal; a wash sale into your IRA is the real loss — never rebuy a harvested security in a retirement account.

Can I sell at a loss in my brokerage account and rebuy the same fund in my IRA or 401(k)?

No — this is the single most damaging mistake in tax-loss harvesting, so it's worth being blunt about. The wash-sale rule applies across ALL your accounts, including your IRAs and your 401(k), and even your spouse's accounts. Worse, when the rebuy lands in an IRA, the disallowed loss can't be added to the IRA's basis (an IRA has none for this purpose), so the deferral mechanism fails and the loss is gone permanently (Revenue Ruling 2008-5). This is why two everyday habits deserve a pause when you harvest: automatic dividend reinvestment and automatic recurring investing — if either drops the harvested fund into any of your accounts inside the 30-day window, it can trip the rule, and into an IRA it's a permanent loss. The fix is simple: when you harvest a fund in your taxable account, don't buy that fund (or a substantially identical one) anywhere — taxable, IRA, or spouse's account — for 30 days, and pause its reinvestment for the month.

Can I just sell one S&P 500 fund and buy a different company's S&P 500 fund?

This is the genuine gray area, and an honest answer admits it's unsettled. The IRS has never defined 'substantially identical' for mutual funds and ETFs — there's no regulation, ruling, or court case on fund-to-fund swaps. What's clear at the edges: swapping two funds that track DIFFERENT indexes (say, a total-market fund for an S&P 500 fund) is safe and beyond dispute; swapping two share classes of the very same fund (or a fund and its own ETF version) is clearly a wash sale. The contested middle is exactly your question — two different companies' funds tracking the IDENTICAL index. One careful camp argues that funds holding virtually identical stocks are arguably 'substantially identical' and a risk; the common-practice camp notes they're legally distinct securities from different issuers and the IRS has never said otherwise. There's no certain answer. The clean way to avoid the question entirely: stick to a replacement that tracks a different index. If you want zero ambiguity, sell and wait the full 31 days before rebuying the original.

Does the wash-sale rule apply to cryptocurrency?

As of tax year 2026, no — the wash-sale rule does not apply to directly held cryptocurrency, which means a crypto investor can sell a coin at a loss and rebuy it immediately and still claim the loss, with no 30-day wait. The reason is technical: the wash-sale law covers only 'stock or securities,' and the IRS classifies crypto as property, not a security, so it falls outside the rule. But state this carefully, because it's actively being legislated. Congress has tried repeatedly to close the gap — a 2021 bill died, a crypto amendment was dropped from the major 2025 tax law, and a fresh bipartisan bill (the Digital Asset PARITY Act) introduced in 2026 would apply the rule to crypto but has not passed. So today there's no enacted law applying the wash-sale rule to spot crypto, but the rule could change with little warning — verify the current status before relying on it. Two cautions: this carve-out is only for directly held crypto (crypto stocks and certain crypto funds are securities and the rule applies to them normally), and new crypto tax-reporting forms now make this activity far more visible to the IRS.

Is tax-loss harvesting a loophole? Will it get me audited?

No on both counts. The rules that make tax-loss harvesting work are spelled out in IRS Publication 550 — it's the IRS's own material. The wash-sale rule, the thing people fear, is the IRS deliberately drawing the line of what's allowed; harvesting a loss and respecting the 30-day boundary is following the instructions, not evading them. This is so mainstream that it's fully automated — most major robo-advisors harvest losses daily, and wealth managers do it as a routine service for clients. The only people who run into trouble are those who try to be too clever about the 30-day rule (rebuying the identical thing too soon, especially in an IRA), and even then the usual consequence is a deferred loss, not an audit. Done the straightforward way — sell a loser, buy a different-index replacement, keep it out of your IRA for a month — it's one of the most ordinary moves in personal taxation.

How much money does harvesting a loss actually save me?

Less than the headline number suggests, because harvesting mostly DEFERS tax rather than erasing it — and being honest about this protects you from overpaying for it. A harvested loss does three jobs in order: it cancels your capital gains dollar-for-dollar, then up to $3,000 a year offsets your ordinary income (with the rest carrying forward indefinitely). But here's the catch: buying a replacement at a lower price gives you a lower cost basis, so your future gain is bigger by exactly the loss you took — the bill mostly moves to later, it doesn't vanish. The real, permanent benefit comes from three things: the time value of deferring the tax, the rate arbitrage of deducting at your high ordinary rate now versus paying the lower capital-gains rate later, and the chance the deferred gain is never taxed (if you sell in a 0% year or hold until death, when the basis resets for your heirs). Concretely, Maya's robo 'banked $380' in losses, which sounds like $380 saved — but the real permanent benefit was closer to $34, plus some deferral value. For a high earner like the Okonkwos, a single big harvest saved $4,434 in a year. Real, useful, scales with your bracket — but rarely the windfall it's pitched as.

My broker's 1099 shows a 'wash sale' I didn't even know I made — what happened?

You almost certainly tripped the rule by accident, most often through automatic dividend reinvestment or recurring auto-investing — a scheduled purchase quietly rebought a fund you'd sold at a loss inside the 30-day window. Your broker tracks wash sales automatically within a single account for the identical security and flags them on Form 1099-B with the code 'W,' deferring the disallowed piece onto your remaining shares. In that case it's automatic, usually small, and not a sign you did anything wrong — it's a deferral, and your tax software handles it. The thing your broker CAN'T see is a wash sale you created across accounts — a loss in your taxable account paired with a buy in your IRA, at another brokerage, or in your spouse's account — and tracking those is legally your responsibility. The lesson for next time: when you harvest a fund, pause its dividend reinvestment and auto-investing for the month, and don't rebuy it anywhere — especially not in an IRA, where the loss would be permanent. (The full read of the 1099-B and its codes is Lesson 43.)

Should I bother doing this myself, or just let my robo-advisor handle it?

It depends on your accounts and your bracket, and for many people the honest answer is 'let the robo do it' or 'don't bother yet.' First, the gate: harvesting only works in a taxable brokerage account — if everything you own is in a 401(k), IRA, or HSA, there's nothing to harvest, full stop. If you do have a taxable account, the benefit scales with your tax bracket (it saved Maya $720 and the Okonkwos $4,434 from the same kind of move) and with how much real loss you have (down years are harvest season; rising markets offer little). If you want it handled automatically and wash-sale-aware, a robo-advisor does daily harvesting for about 0.25% a year — that's the easy path for most people. If you do it yourself, keep it simple: in a down year, sell a loser, buy a different-index replacement the same day, take the $3,000 against income, and keep the harvested fund out of your IRA for a month. What you should NOT do is pay a 1%-of-assets advisor mainly for harvesting (for the Okonkwos that's $5,450 a year, likely more than the harvesting adds) or distort a good portfolio chasing a small tax move — don't let the tax tail wag the dog.

This is the L39 interactive, and it makes the whole lesson concrete on your own numbers rather than a character's, in two connected parts. The first part prices a harvest: enter the size of the loss you're harvesting, mark whether it's short- or long-term, enter your realized short-term and long-term capital gains for the year, and your two tax rates (your ordinary rate and your long-term capital-gains rate), and it computes — live, in the order the IRS actually applies — how much tax the loss saves you this year. It nets the loss against same-type gains first (a long-term loss against long-term gains, a short-term loss against short-term gains), lets any leftover cross to the other type, then applies up to $3,000 against your ordinary income, and it shows the leftover that carries forward to future years. The second part is the wash-sale checker, and it's where the lesson's central warning becomes vivid: two toggles ask whether you rebought the same or a substantially identical security within 30 days, and — if so — whether the rebuy was inside an IRA. Leave both off and your harvest is clean and the full saving stands. Flip the first on and the widget shows the loss disallowed for this year but deferred onto your replacement's basis (you get it back later). Flip the second on too and it shows the IRA trap — the loss permanently destroyed, this year's saving dropping to zero. It's pre-filled with the Okonkwos' case from §2.3 — a $30,000 loss against $18,000 of long-term gains at a 35% ordinary rate and an 18.8% capital-gains rate, which reproduces the lesson's $4,434 of tax saved and $9,000 carried forward — so you can watch the tool produce the exact figures from the lesson before you clear it and enter your own. Try setting your long-term rate to 0% and watch the value of offsetting gains vanish, the way it does for investors in the 0% bracket; try flipping the IRA toggle and watch a $4,434 saving collapse to nothing. Everything recalculates the instant you type, it runs entirely in your browser with nothing saved or sent anywhere, and the rates are illustrations of how the math works, not tax advice. Use it to turn 'is this worth it, and did I just ruin it?' into two clear answers built from your own facts.