Tax-Loss Harvesting

Tax-loss harvesting is the practice of selling an investment that sits below its purchase price, realizing the loss, and spending it against the tax code. Realized losses first cancel realized gains of the same character: short-term losses against short-term gains, long-term against long-term. Leftover losses cross over to the other bucket, and up to $3,000 of whatever remains deducts against ordinary income each year, $1,500 for married filing separately. Unused losses carry forward indefinitely.

The paperwork lives on Form 8949 and Schedule D, and most brokerages prefill the arithmetic every January. The one rule that bites is the wash-sale rule: rebuy the same or a substantially identical investment within 30 days before or after the sale, and the IRS cancels the loss. The fix is boring — swap into a similar fund tracking a different index, and stay invested.

The netting runs in an order the IRS fixed decades ago. Short-term losses cancel short-term gains first, long-term losses cancel long-term gains first, and only after each bucket nets out do the leftovers cross. A $6,000 short-term loss against a $4,000 long-term gain leaves the gain fully canceled and $2,000 of loss remaining, which then deducts against ordinary income up to the $3,000 cap. The remainder carries forward to next year's Form 8949.

The wash-sale rule is the enforcement mechanism. Selling a fund at a loss and buying the same fund, or one substantially identical, within 30 days before or after the sale disallows the loss, and the disallowed amount folds into the cost basis of the replacement shares instead of vanishing. The window runs both directions, so a purchase made three weeks ago counts against a sale made today. Per IRS Revenue Ruling 2008-5, buying the fund inside a spouse's account or your own IRA counts too.

The standard implementation is a swap, not an exit. Selling an S&P 500 fund at a loss and buying a total-market fund the same afternoon keeps the portfolio invested while the loss stays bankable, because the two funds are similar but not substantially identical. After the 31st day, the investor can swap back or simply stay put. The loss waits on the tax return; the market exposure never left.

Volatility is a liability on the statement and an asset on the tax return, and harvesting is the exchange rate between the two. A taxable brokerage account compounds under an annual tax drag that a 401(k) never pays, and harvested losses are the one lever that pulls the bill down without changing a single holding. A $3,000 deduction at the 24% bracket is $720 a year, collected for doing something the drawdown already did.

I watched a colleague named Brent (yes, that Brent) sell a losing position to cash in a correction, then rebuy the identical fund three weeks later to be safe. The wash-sale rule cancelled the loss, the market recovered without him during the paperwork gap, and the tax return showed nothing. He managed to pay the costs of both strategies and collect the benefit of neither.

The highest-leverage thing most Americans can do is harvest losses whenever a taxable holding trades below basis, swap into a different fund rather than cash, and let the carryforward absorb future gains. Run the savings with the tax-loss harvesting calculator and net the gains and losses with the portfolio tax calculator. The trough is survivable; the paperwork error at the trough rarely is.