The Wash-Sale Rule
This lesson prevents a specific, expensive surprise. You sell an investment at a loss to claim the tax benefit — then buy it right back because you still like it — and discover the IRS has voided the loss entirely. That's the wash-sale rule, and it exists to stop people from booking tax losses without actually giving up their position. Learn it now and you'll never trip it by accident.
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 loss is disallowed. That's a 61-day window centered on your sale date. The government's view is simple: if you're back in essentially the same position that fast, you never really took the loss, so you don't get to deduct it.
Here's the part that softens the blow: a disallowed wash-sale loss isn't gone forever. It gets added to the cost basis of the replacement shares, so you recover the benefit when you eventually sell those. The rule delays your deduction; it doesn't confiscate it. That's important — a wash sale is a timing headache and a record-keeping mess, not a permanent loss of the tax break.
The same stock or the same fund is clearly identical. But is one S&P 500 index fund 'substantially identical' to a different company's S&P 500 fund? The IRS has never drawn a bright line, and that ambiguity is exactly where careful investors tread lightly. Many people sidestep the whole question by replacing a sold fund with one tracking a DIFFERENT index — similar exposure, clearly not identical — but understand you're navigating a judgment call, not a settled rule.
The trap most people don't see: the window spans ALL your accounts, and your spouse's. Sell a stock at a loss in your taxable account and rebuy it in your IRA within the window, and you've triggered a wash sale — with a brutal twist, because a loss washed by an IRA purchase can be lost permanently, with no basis adjustment to recover it. Automatic dividend reinvestment and even certain options trades on the same name can spring the trap too. Coordinate across every account you and your spouse hold.
None of this should scare you off claiming legitimate losses — it should just make you deliberate. Turn off automatic reinvestment on a holding you're harvesting, wait out the window or buy a genuinely different replacement, and check your other accounts before you click. Do that, and the wash-sale rule becomes a box you check rather than a bill you didn't expect. The next lesson puts this discipline to work on purpose.
Sell at a loss and rebuy the same thing within 61 days and the deduction is deferred, the basis shifts, and an IRA rebuy can cost you the loss for good. It's not a reason to fear harvesting losses — it's the one rule you respect so that harvesting them actually works.
Not financial advice · Educational only