Selling an investment at a loss on purpose sounds like the opposite of good investing advice. Tax-loss harvesting is the one situation where it can genuinely make sense. You use a paper loss to reduce a tax bill, without permanently abandoning the market position that generated it.
The mechanics of tax-loss harvesting
Tax-loss harvesting means selling an investment that has dropped below its purchase price to realize a capital loss. That loss can then offset capital gains elsewhere in your portfolio. If losses exceed gains in a given year, the IRS allows up to $3,000 of the excess loss to offset ordinary income each year. Any remaining loss carries forward to future tax years indefinitely.
For an investor sitting on both a large gain in one position and a loss in another, harvesting the loss can meaningfully reduce or eliminate the tax owed on the gain. The strategy is most useful in taxable brokerage accounts. It does nothing in a 401(k) or IRA. Gains and losses inside tax-advantaged accounts are not taxed as they occur in the first place.
The wash-sale rule that trips people up
The IRS wash-sale rule disallows the tax loss if you repurchase the same or a “substantially identical” security within 30 days before or after the sale. That is a 61-day window in total.
Buying back the exact same fund the next day to keep the same market exposure does not work. The loss gets disallowed and added to the cost basis of the new position instead of being usable immediately. Investors who want to stay invested typically swap into a similar but not identical fund. Moving from one broad-market index fund to a comparable one from a different provider maintains market exposure through the 61-day window without violating the rule.
The rule applies across all of your accounts. That includes your spouse’s accounts and IRAs, not just the account where the sale happened. That detail catches households with investments split across multiple brokerages off guard. If you sell a fund in your taxable account and your spouse buys the same fund in their IRA within 30 days, the loss is disallowed.
When it is worth the effort
Tax-loss harvesting delivers the most value in years with large realized capital gains to offset. It also helps investors in higher tax brackets, where the value of each dollar of deduction is greater. New York Life’s retirement planning materials note that harvesting is generally more valuable earlier in the calendar year and during volatile markets. Temporary dips create more opportunities to realize losses without changing your underlying long-term allocation.
For a portfolio that is already well-diversified and rarely traded, the opportunities for harvesting are naturally fewer. There is less turnover generating gains to offset in the first place. In that case, it is worth checking during periods of market weakness rather than trying to force the strategy on a schedule.
There is also a risk of overdoing it. Harvesting a loss means you reset your cost basis lower. That lowers your current tax bill but increases the gain you will owe tax on when you eventually sell. If you harvest losses every year regardless of need, you may be deferring taxes rather than eliminating them. The strategy works best when you have real gains to offset, not as a standing annual habit.
How it fits with rebalancing
Tax-loss harvesting pairs naturally with portfolio rebalancing. When you rebalance, you sell assets that have grown and buy assets that have shrunk. In a taxable account, that triggers capital gains. Harvesting losses in other positions can offset those gains, making the rebalance more tax-efficient.
The two strategies work together. Rebalancing keeps your allocation on target. Harvesting keeps the tax cost of rebalancing down. Managing a portfolio around gains and losses ties directly into broader rebalancing decisions. See this guide to rebalancing a portfolio without triggering extra taxes for how the two work together.
Tax-loss harvesting will not turn a losing investment into a winning one. It only changes when and how much tax gets paid on the portfolio as a whole. That is a modest but real benefit for investors who already have taxable gains to manage. For anyone with a simple buy-and-hold portfolio and no realized gains, the strategy rarely moves the needle enough to justify the complexity.
