Pro-rata rule
The IRS rule that makes Backdoor Roth conversions partly taxable if you have pre-tax IRA balances.
Why it matters
The rule treats all traditional, SEP, and SIMPLE IRA balances as a single pool for conversion purposes. Rolling pre-tax IRAs into a 401(k) before converting sidesteps it, if your plan accepts rollovers in.
See also
Educational only — not financial, tax, or legal advice.