Tax-loss harvesting

If you have investments in a taxable brokerage account, tax-loss harvesting is an advanced but legal strategy where you realize paper losses on purpose to offset future taxes, without meaningfully changing your investment exposure.

How it works

Say you bought $10,000 of a total stock market ETF. It drops to $8,500. You sell it, realizing a $1,500 capital loss. You immediately buy $8,500 of a similar but not 'substantially identical' fund — say, a different provider's total stock ETF tracking a slightly different index. You still own roughly the same market exposure; your risk and return look nearly identical. But now you have a $1,500 loss on your tax return.

What you do with the loss

• Offsets capital gains dollar-for-dollar in the current year.
• Up to $3,000 of excess losses can offset ordinary income (wages, interest) each year.
• Any remaining loss carries forward indefinitely for future years.

When to do it

Only matters in taxable brokerage accounts (not IRAs or 401ks — they're already tax-advantaged). Most useful during market drawdowns, when losses exist to harvest. Some brokerages (Wealthfront, Betterment, Fidelity) do this automatically.

A worked example with real dollars

Say you invested $60,000 in a total US market ETF in January, and by October a rough market has it sitting at $51,000. You sell, realizing a $9,000 loss, and immediately buy $51,000 of a different broad US fund tracking a different index — say, swapping an S&P 500 fund for a total market fund. Your market exposure is essentially unchanged. Come tax time, suppose you also sold some old company stock this year with $4,000 of gains: the harvested loss wipes those out entirely, then knocks $3,000 off your ordinary income, and the remaining $2,000 carries forward to next year. If you are in the 24% federal bracket with 5% state tax, the income offset alone is worth about $870 this year, and the erased capital gains save another $600 at the 15% rate — roughly $1,470 of real tax savings for two trades that took ten minutes.

What harvesting actually buys you (deferral, mostly)

It is worth being precise about the benefit. When you harvest a loss, your new fund has a lower cost basis — you bought at $51,000 instead of $60,000 — so if it recovers and you eventually sell, the gain is larger by exactly the amount you harvested. Most of the benefit is therefore tax deferral, not tax elimination: you save at today's rates and pay later. Deferral is still genuinely valuable, because the deferred tax stays invested and compounds for you in the meantime, and there are three ways it becomes permanent savings: you offset ordinary income (taxed up to 37%) with losses that would otherwise offset capital gains (taxed at 15 to 20%), a rate arbitrage worth real money; you donate the appreciated shares to charity, which erases the gain; or you hold until death, when current law steps up the basis for your heirs and the deferred gain vanishes entirely.

Common mistakes that void the benefit

• Tripping the wash sale with automation: dividend reinvestment or a scheduled 401k purchase of the same fund inside the 30-day window disallows a chunk of the loss. Pause auto-reinvest in the harvested fund first, and remember the rule looks across all your accounts, including IRAs and a spouse's accounts.
• Swapping into something 'substantially identical': selling one S&P 500 ETF and buying another provider's S&P 500 ETF tracking the same index is widely considered too close for comfort. Change the index, not just the ticker.
• Harvesting trivial losses: a $200 loss saves perhaps $50 of tax and clutters your records with a new tax lot. Many practitioners set a floor — only harvest when a lot is down at least $1,000 or several percent.
• Sitting out of the market during the swap: staying in cash for 30 days to avoid the wash sale is far more dangerous than the rule itself. Markets often rebound sharply after drops; buy the replacement fund the same day you sell.
• Forgetting state quirks: a few states do not allow loss carryforwards the way federal law does, which slightly reduces the value for high earners in those states.

Should you bother? A quick sizing test

Harvesting rewards people with meaningful taxable balances, ongoing gains to offset, and high marginal rates. If your taxable account is under roughly $25,000, the dollars involved rarely justify the added complexity — focus on contributions instead. If you hold six figures in a taxable account and sit in the 32%+ bracket, harvesting a bad year can be worth thousands, and automated services from Wealthfront, Betterment, Schwab, and Fidelity will run the process for you at little or no extra cost. Either way, never let the tax tail wag the investment dog: the portfolio you hold after every harvest should be one you would happily own anyway.

The bottom line

Tax-loss harvesting is one of the few genuinely free-ish lunches in taxable investing, but it is a side dish, not the meal. Done correctly it converts market downturns into a modest, recurring tax subsidy — typically worth a few tenths of a percent per year on the harvested balance, more in volatile years and high brackets. Done carelessly it triggers wash sales, clutters your records, and tempts you into holding funds you do not actually want. If your situation is simple, let an automated service handle it or skip it entirely without guilt; the strategy ranks well below savings rate, asset allocation, and low fees on the list of things that determine whether you retire comfortably.

One final housekeeping note: keep every trade confirmation and let your brokerage track the cost basis of each lot. When you harvest across multiple lots purchased at different times, choosing 'specific identification' as your cost basis method — rather than the default average cost — lets you sell exactly the lots with losses while leaving the gainers untouched, which is where much of the strategy's precision comes from.