Why Losing Money Can Still Be a Win
Nobody invests hoping to lose money, but once a loss has already happened in a taxable brokerage account, you can still get something out of it. Tax-loss harvesting means selling an investment that has dropped below what you paid for it, locking in that loss on paper, and using it to reduce your tax bill. The loss first offsets any capital gains you realized elsewhere that year — dollar for dollar. If your losses exceed your gains, up to $3,000 of the leftover amount can be deducted against your ordinary income, and anything beyond that carries forward to future tax years indefinitely.
The Wash-Sale Rule Trap
Here is where most people trip up. The IRS wash-sale rule disallows your loss if you buy the same security, or one the IRS considers “substantially identical,” within 30 days before or after the sale. Sell a losing S&P 500 index fund and immediately rebuy the identical fund the next day, and your loss is disallowed for that tax year. The fix is simple: swap into a similar but not identical fund, such as a total-market index instead of an S&P 500 index, for 31 days before moving back if you want. This keeps your market exposure roughly intact while still banking the tax loss.
Timing It Right
Tax-loss harvesting is often framed as a December activity, but market dips happen all year, and waiting until year-end means you might miss earlier opportunities or rush decisions during a volatile week. A better approach is to check your taxable accounts quarterly, or whenever a position drops at least 10 to 15% below your cost basis, and decide then whether harvesting makes sense given your other gains for the year. Robo-advisors and some brokerage platforms now automate this process daily, which can meaningfully boost after-tax returns over time without you lifting a finger.
What It Will Not Do
Tax-loss harvesting does not create free money; it defers taxes by lowering your cost basis on the replacement investment, which means a larger taxable gain later if you eventually sell at a profit. The real benefit comes from the time value of money: a dollar of tax savings today, reinvested, is worth more than the same dollar paid in taxes years from now. It is most powerful in taxable brokerage accounts, since retirement accounts like 401(k)s and IRAs are already tax-advantaged and gains or losses inside them have no tax consequence.
Who Should Bother
If you only invest through retirement accounts, this strategy is irrelevant to you. But if you hold individual stocks or ETFs in a regular brokerage account, especially after a volatile year, it is worth a look before December 31. Check your year-to-date realized gains, scan your holdings for anything sitting at a loss, and talk to a tax professional before executing trades close to a deadline, since the wash-sale rule also applies across your IRA if you try to rebuy there. Used consistently, tax-loss harvesting is one of the few tax strategies that costs you nothing but a little attention.
