Tax-Loss Harvesting: A Complete Guide
A down market hands you a gift most investors ignore: realized losses you can use to cut this year's tax bill — without abandoning your investment plan.
Don't have time? Here's what you need to know:
- 1Harvesting realizes a loss to offset capital gains plus up to $3,000 of ordinary income per year, carrying the rest forward.
- 2Immediately reinvest in a similar-but-distinct fund to stay invested while banking the tax benefit.
- 3The wash-sale rule disallows the loss if you rebuy a substantially identical security within 30 days before or after.
- 4Harvesting only works in taxable accounts and is most valuable in volatile markets and higher-income years.
Turning a Paper Loss Into a Tax Asset
Tax-loss harvesting is the practice of intentionally selling an investment that has dropped below your purchase price to realize a capital loss, then putting that loss to work on your tax return. The loss isn't money you've thrown away — it's a tax asset. It offsets capital gains dollar for dollar, and if your losses exceed your gains, you can deduct up to $3,000 of the excess against ordinary income each year, carrying any remainder forward to future years indefinitely.
The elegant part is that you don't have to leave the market to do it. Immediately after selling the losing position, you buy a similar (but not substantially identical) investment, so your overall market exposure barely changes while you bank the tax benefit. You stay invested, you keep your asset allocation, and you harvest a deduction the IRS lets you use against income that would otherwise be fully taxed.
How a Harvest Actually Works
Suppose you bought a broad-market ETF and it's now down $8,000 from your cost basis. You sell it, realizing an $8,000 capital loss. If you also realized $5,000 of gains elsewhere this year, the loss wipes those out entirely and leaves $3,000 — exactly the amount you can deduct against ordinary income. At the same moment, you buy a comparable fund that tracks a different but similar index, so your portfolio stays roughly where it was.
Crucially, harvesting a loss lowers your cost basis in the replacement holding. That means you're partly deferring tax, not erasing it — if the replacement recovers and you later sell, the gain is larger. The benefit comes from the time value of paying tax later, from offsetting gains taxed at high rates with losses, and from the annual $3,000 ordinary-income deduction, which permanently shelters income at your top rate.
| Use of the loss | How much per year | What happens to excess |
|---|---|---|
| Offset capital gains | Unlimited | Fully used first |
| Deduct against ordinary income | Up to $3,000 | Carried forward |
| Carryforward to future years | Indefinite | Until fully used |
Tip: Harvest losses in higher-income years, when offsetting gains and deducting ordinary income are worth the most. The deduction is more valuable the higher your marginal rate.
The Wash-Sale Rule You Must Respect
The one rule that can void your harvest is the wash-sale rule. If you buy the same or a "substantially identical" security within 30 days before or after selling at a loss, the IRS disallows the loss for now and adds it to the basis of the replacement shares. The 30-day window runs in both directions, creating a 61-day danger zone around the sale, and it applies across all your accounts — including a spouse's and an IRA.
The standard workaround is to replace the sold fund with a similar-but-distinct one: sell an S&P 500 ETF and buy a total-market ETF, or swap one provider's broad index fund for another tracking a different index. They give nearly identical exposure without being substantially identical. Two cautions: don't let automatic dividend reinvestment quietly rebuy the sold fund inside the window, and remember a repurchase in your IRA can still trip the rule. When unsure, wait the full 31 days or consult a tax professional.
Important: Turn off automatic dividend reinvestment on a fund you plan to harvest, or a small reinvested purchase within 30 days can trigger a partial wash sale and disallow part of your loss.
When Harvesting Is and Isn't Worth the Effort
Harvesting shines for investors with taxable accounts, meaningful balances, and either current capital gains or high ordinary income to offset. It's most powerful in volatile markets and early in a position's life, before large gains have accumulated. It also pairs naturally with ETFs, whose deep menu of similar-but-distinct funds makes finding a clean replacement straightforward.
It's less useful — or pointless — in a few cases. There's nothing to harvest inside a Roth IRA or 401(k), since those accounts have no taxable gains or losses. If you have no gains and limited ordinary income, the benefit is capped at the modest $3,000 deduction. And don't let the tax tail wag the investment dog: harvesting that pushes you into a worse fund, higher costs, or a portfolio you'll regret isn't worth a small deduction. Keep the investment thesis first and treat the tax benefit as a bonus.
Frequently Asked Questions
How does tax-loss harvesting save money?
By converting a paper loss into a deduction. The realized loss offsets capital gains dollar for dollar, and up to $3,000 of any excess loss can be deducted against ordinary income each year, with the rest carried forward. You reinvest in a similar fund to stay in the market, so you capture the tax benefit without changing your strategy.
How much can I deduct from tax-loss harvesting?
Losses first offset your capital gains with no dollar limit. If losses still exceed gains, you can deduct up to $3,000 of the excess against ordinary income per year. Any remaining loss carries forward indefinitely to offset future gains or another $3,000 of income in later years.
Doesn't tax-loss harvesting just defer the tax?
Partly. Selling at a loss lowers your basis in the replacement holding, so a future sale produces a larger gain. The benefit comes from offsetting gains taxed at high rates today, the annual $3,000 ordinary-income deduction, and the time value of paying tax later. The basis at death can also erase the deferred gain entirely.
Can I harvest losses in my IRA or 401(k)?
No. Tax-advantaged accounts have no taxable capital gains or losses to harvest, so the strategy doesn't apply there. Worse, buying a substantially identical security in your IRA within 30 days of a taxable-account loss sale can trigger the wash-sale rule and disallow the loss.
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Alex Harrington
CFA Level II Candidate, Finance & Economics
Alex Harrington is an independent ETF researcher and personal finance writer with over 8 years of experience analyzing exchange-traded funds. A CFA Level II candidate with a background in economics, Alex has reviewed 800+ ETFs and helped thousands of beginners build their first investment portfolios through clear, jargon-free education.
This content is for educational purposes only and does not constitute financial advice. Past performance does not guarantee future results. Consult a licensed financial advisor before making investment decisions.