Tax-Loss Harvesting: How to Turn Investment Losses Into Tax Savings

How Tax-Loss Harvesting Works

Tax-loss harvesting is the practice of selling an investment that has declined below its purchase price to realize a capital loss, which can then offset capital gains elsewhere in your portfolio — or, up to $3,000 per year, offset ordinary income. The key is that you immediately reinvest the proceeds in a similar (but not identical) investment, so you maintain essentially the same market exposure and long-term investment strategy.

Here's a simple example: You bought 100 shares of a large-cap ETF at $100 per share ($10,000 total). The market drops and the ETF is now worth $8,000. You sell — realizing a $2,000 capital loss. You immediately buy a similar ETF tracking a different index with the $8,000. Your portfolio value hasn't changed, but you've generated a $2,000 tax loss. If you're in the 20% long-term capital gains bracket, that $2,000 loss is worth $400 in actual tax savings.

Losses first offset gains of the same character (short-term losses against short-term gains; long-term losses against long-term gains). Excess losses can then be applied against gains of the opposite type. Any remaining net capital loss offsets up to $3,000 of ordinary income. Losses beyond that carry forward indefinitely to future tax years.

The Wash-Sale Rule: The Critical Constraint

The IRS wash-sale rule prohibits claiming a capital loss if you buy a "substantially identical" security within 30 days before or after the sale — a 61-day window in total. If you violate the wash-sale rule, the loss is disallowed and added to the cost basis of the replacement shares (effectively deferring, not eliminating, the tax benefit).

What counts as "substantially identical" is not always clear-cut. The same fund is obviously identical. A different ETF tracking the same index is generally considered substantially identical (e.g., selling Vanguard S&P 500 ETF and buying iShares S&P 500 ETF). However, selling a total US market ETF and buying an S&P 500 ETF is generally considered permissible — as is selling a US large-cap fund and buying an international equivalent.

Short-Term vs. Long-Term Losses: Which Is More Valuable?

The tax value of a harvested loss depends on what type of gain it offsets:

• Short-term losses offset short-term gains first. Short-term gains are taxed as ordinary income — up to 37% — making a short-term loss worth up to $0.37 per dollar in the highest bracket.
• Long-term losses offset long-term gains first. Long-term capital gains rates are 0%, 15%, or 20%, making a long-term loss worth up to $0.20 per dollar.

For investments held less than a year, harvesting losses has greater tax value — but most tax-loss harvesting involves longer-held positions at long-term rates. Even at 15–20%, consistent harvesting over years of market volatility can compound into meaningful tax savings and higher after-tax returns.

Automated Tax-Loss Harvesting

Robo-advisors like Betterment and Wealthfront pioneered automated daily tax-loss harvesting — scanning portfolios for harvesting opportunities every day rather than waiting for end-of-year reviews. Because market volatility creates harvesting opportunities throughout the year, daily monitoring can significantly increase the amount of losses captured.

These platforms automatically sell a losing position, immediately buy a substitute, wait 31 days, and optionally switch back — all while managing wash-sale compliance across all accounts linked to the platform. Research from Wealthfront suggests their automated harvesting adds approximately 0.48% to 1.55% in annual after-tax returns for taxable accounts, depending on account size and market conditions.

For DIY investors, the same strategy works manually — it simply requires discipline to monitor your portfolio during market downturns and act quickly. The largest harvesting opportunities arise during sharp market selloffs: the early pandemic crash of 2020 and the 2022 bear market both offered exceptional harvesting windows for investors who were watching.

Important Limitations

Tax-loss harvesting only applies to taxable accounts — losses in IRAs and 401(k)s have no immediate tax impact. Additionally, harvesting defers taxes rather than eliminating them: by lowering your cost basis, you create a larger gain when the replacement investment is eventually sold. The benefit is greatest when you expect to be in a lower bracket on the future gain, hold assets until death (when heirs receive a step-up in basis), or donate appreciated shares to charity.