Wash sale rule
A tax rule that disallows a loss if you buy the same or substantially identical security within 30 days.
Why it matters
The IRS wash sale rule prevents harvesting a tax loss while staying in essentially the same position. The disallowed loss is added to the cost basis of the new purchase, so it's deferred rather than lost. Applies across all accounts you or a spouse controls.
See also
Educational only — not financial, tax, or legal advice.