Tax-loss harvesting is the practice of selling an investment that has dropped in value to realize the capital loss for tax purposes, then immediately reinvesting the proceeds in something similar so your overall portfolio stays roughly the same. The realized loss can offset capital gains elsewhere in your portfolio — and up to $3,000 of ordinary income per year if losses exceed gains.
It only matters in taxable accounts. Inside an IRA, 401(k), or Roth account, gains and losses are not taxed in the year they happen, so there’s nothing to harvest. But for taxable brokerage accounts, tax-loss harvesting can be a meaningful and entirely legal way to reduce your tax bill while keeping your investment plan intact.
How it works
Imagine you own 100 shares of a total stock market ETF you bought for $20,000. The market drops, and the position is now worth $17,000 — an unrealized loss of $3,000. The loss is “unrealized” because you haven’t sold yet.
To harvest the loss:
- Sell the position, realizing the $3,000 capital loss
- Use the proceeds to immediately buy a similar but not “substantially identical” investment — e.g., a different total market ETF from a different provider, or an S&P 500 ETF
- Hold that replacement until at least 31 days have passed (the wash-sale rule, explained below)
- After 31 days, you can swap back to your original holding if you prefer — though most people just keep the replacement
The result: your portfolio is essentially unchanged in market exposure, but you now have a $3,000 capital loss to use against gains or income on your tax return.
How the loss reduces your taxes
Capital losses follow this hierarchy:
- Offset short-term capital gains first (held less than a year, taxed at ordinary income rates)
- Then offset long-term capital gains (held more than a year, taxed at preferential rates of 0%, 15%, or 20%)
- Then offset up to $3,000 of ordinary income per year (interest, wages, etc.)
- Then carry forward to future years indefinitely until used up
The most valuable use is offsetting short-term gains, which would otherwise be taxed at your full ordinary income rate (potentially 22%, 24%, 32%, or higher). A $3,000 loss against a 24%-bracket short-term gain saves $720 in tax.
The next-most-valuable use is offsetting ordinary income up to $3,000 per year. At a 24% bracket, that’s a $720 tax saving each year that the harvested loss is applied.
Offsetting long-term gains is the least valuable use because long-term capital gains rates are already lower — 15% for most people, 0% in some cases. A $3,000 loss against a 15% long-term gain saves $450.
The wash-sale rule
This is the most important rule in tax-loss harvesting. The IRS will disallow a loss if you buy “substantially identical” securities within 30 days before or after the sale — a 61-day window centered on the sale date.
The rule applies across all your accounts (and your spouse’s, and an IRA you control), so you can’t harvest a loss in your taxable account while simultaneously buying the same security in your IRA or a spouse’s account. The disallowed loss isn’t lost permanently — it’s added to the cost basis of the replacement — but it’s no longer available as an immediate tax offset.
“Substantially identical” is the operative phrase, and it’s not perfectly defined. Clearly safe distinctions:
- Two different ETFs tracking different indexes (e.g., S&P 500 ETF for total stock market ETF) — safe
- Two ETFs tracking the same index from different providers (e.g., VTI and SCHB, both total U.S. market) — widely viewed as safe but a small gray zone
- Selling a stock and buying call options or other derivatives on the same stock — not safe
- Selling and buying back the exact same fund — clearly disallowed
In practice, most investors maintain a list of “tax-loss harvesting partners” — pairs of similar but not identical funds they swap between. For total U.S. stock market exposure: VTI and SCHB. For total international: VXUS and IXUS. For S&P 500: VOO and IVV. After 31 days, you can swap back to the original if you want.
When tax-loss harvesting is most valuable
- You have meaningful taxable investment accounts. The strategy doesn’t apply to IRAs or 401(k)s
- You have realized capital gains or expect to in the near future. Without gains to offset, you can only use $3,000/year against ordinary income
- You’re in a higher tax bracket. The dollar value of a tax saving is your bracket rate — the higher your bracket, the more valuable the harvest
- The market has dropped. Significant losses to harvest typically appear in market downturns — the worse the drop, the bigger the harvesting opportunity
- You have many lots with different cost bases. Specific-share identification lets you sell only the lots that have lost money, leaving the gainers alone
When it’s not worth doing
- The loss is small. Harvesting $200 of loss to save $30–$50 in taxes isn’t worth the effort
- You’ll trigger a wash sale anyway. If you have automatic dividend reinvestment turned on or you contribute to your taxable account regularly, those purchases can accidentally trigger a wash sale — check the rules carefully
- You have unrealized gains in the same fund from many older lots. Selling a recently-bought-at-a-loss lot in a fund where most of your other shares have large gains may inadvertently trigger gain realization on the older lots if your broker uses average-cost basis
- Your tax rate is at 0% on long-term gains. If you’re in the 0% capital gains bracket, harvesting losses against future gains is less valuable than realizing those gains tax-free instead
The cost-basis trap
Tax-loss harvesting doesn’t eliminate tax — it defers it. When you harvest a loss and buy a replacement, the replacement’s cost basis is the lower current price. If markets recover (as they typically do), the eventual sale of the replacement will trigger a larger gain than the original would have.
This is fine as long as:
- You’re saving tax now at a higher rate than you’ll pay later (likely if you’re working and harvest losses against ordinary income)
- You hold the replacement for the long term — the deferred gain compounds against the savings from the immediate deduction
- You eventually use a stepped-up basis at death (heirs receive the replacement at its market value at death, eliminating the deferred gain entirely)
If you instead plan to sell the replacement quickly at a similar tax rate to today’s, harvesting saves less than it appears.
Practical execution
Specific-share identification
By default, most brokers use first-in-first-out (FIFO) cost basis when you sell. For tax-loss harvesting, switch your account to specific-share identification so you can choose which lots to sell — specifically the ones with losses, leaving the lots with gains alone. Most major brokers support this; you typically pick the lots at sale time.
Turn off automatic dividend reinvestment in the harvested fund
If a dividend reinvests in the same fund within 30 days of your loss sale, it triggers a partial wash sale. Either turn off DRIP for that fund during the 61-day window, or have dividends paid as cash.
Watch the calendar
Late December is a popular time to harvest because it allows the loss to apply to the current tax year. But you can harvest any time the market has dropped. Some investors check periodically throughout the year and harvest opportunistically when meaningful losses appear.
Robo-advisors handle this automatically
Services like Wealthfront, Betterment, and Schwab Intelligent Portfolios automatically tax-loss harvest within client accounts — usually daily checks for losses meeting their threshold. If you want the benefits without the hassle, this is one of the genuine advantages of automated platforms over DIY.
Bottom line
Tax-loss harvesting is one of the few strategies that can quietly add tens of thousands of dollars in lifetime value with no change to your underlying investment plan. It doesn’t apply to retirement accounts, only to taxable ones — but for people with meaningful taxable investments, it’s worth understanding and using.
The strategy isn’t about timing the market or picking better investments. It’s about turning unavoidable market drops into useful tax assets — and that’s about the only free lunch in investing.
Further Reading
- Index Funds vs. Actively Managed Funds
- ETFs Explained
- Tax-Efficient Withdrawal Order in Retirement
- Asset Allocation: How to Build Your Mix
- Mutual Funds vs. ETFs
- Understanding Investment Risk
This article is for general educational purposes only and does not constitute tax or investment advice. Tax-loss harvesting has specific rules and tax consequences — consult a qualified tax professional before implementing.