Tax-Loss Harvesting: Turning Paper Losses Into a Tax Benefit
A position that's down is annoying — but in a taxable account it's also a tool. Selling it realizes a capital loss that cuts your tax bill this year. The catch is that harvesting defers tax rather than erasing it, and one common mistake — rebuying too soon — can void the loss entirely.
- The answer: realize the loss, use it against your capital gains (short-term against short-term first), then up to $3,000 of ordinary income; the rest carries forward indefinitely.
- The trap: if you buy the same or a "substantially identical" security within 30 days before or after the sale, the loss is disallowed (the wash-sale rule). Buy a similar-but-not-identical fund instead.
- The recommendation: treat it as a deferral plus rate arbitrage — offset 37% ordinary income now, pay 15–20% long-term gains later — and never let the tax tail wag the investment dog.
Where the AI summary above gets this wrong
"Sell your losing investments to lower your taxes — tax-loss harvesting reduces what you owe."
That's surface-true. Here's what it misses:
- The wash-sale rule — the single most common mistake. Rebuy the same or a substantially identical security within 30 days before or after the sale and the IRS disallows the loss, folding it into the new lot's basis. It even applies across your IRA and a spouse's accounts.
- It defers, it doesn't erase — reinvesting at a lower basis means a bigger gain later. The tax comes back when you sell, so the real win is timing and rate, not elimination.
- Only $3,000 a year hits ordinary income — losses beyond your gains are capped at $3,000 against ordinary income ($1,500 if married filing separately); the remainder just carries forward.
I'm Jordan, 51, and I harvest losses in my own taxable brokerage account most years there's a dip. It's real money, but it's the most oversold move in personal finance — so let me walk you through what it does, what it costs, and where people trip.
01 What harvesting actually does
Selling an investment for less than you paid in a taxable account realizes a capital loss. That loss offsets your capital gains dollar-for-dollar, and the netting follows a specific order: short-term losses go against short-term gains first, long-term against long-term, and only then do the categories cross over. If your losses exceed all your gains for the year, you can deduct up to $3,000 of ordinary income ($1,500 if married filing separately). Anything still left over carries forward indefinitely to future years.
So a single $10,000 harvested loss might wipe out an $8,000 gain you'd otherwise pay tax on, then knock $2,000 off your ordinary income — all without changing how much of the market you own, because you reinvest the proceeds the same day in a similar fund.
02 The wash-sale rule
This is where most harvests go wrong. The wash-sale rule disallows your loss if you buy the same — or a "substantially identical" — security within 30 days before or after the sale. The disallowed loss isn't gone forever; it's added to the cost basis of the new lot. But you lose the deduction this year, which defeats the point.
The fix is simple: reinvest in a similar-but-not-identical fund. Sell an S&P 500 fund at a loss and buy a total-market or large-cap fund tracking a different index, and you keep essentially the same exposure without triggering the rule. The trap to watch is that the rule spans all your accounts — if you rebuy the identical fund in your IRA or your spouse's account inside that 61-day window, the loss is still disallowed.
The 61-day window runs both directions. If you bought more of the same fund in the 30 days before you sell, that purchase can trigger a wash sale too — not just buying afterward. Check recent automatic reinvestments and dividend purchases before you harvest.
03 Worked example: your tax saved
The rough saving from harvesting a loss is the loss times the tax rate it offsets. Put in how much loss you're harvesting and your marginal rate to see the order-of-magnitude benefit this year.
Shows: the rough tax reduced by harvesting this loss — harvested loss × your marginal rate (note: only up to $3,000 of any net loss can offset ordinary income; beyond that it must offset capital gains or carry forward). Ignores: the wash-sale rule mechanics, the basis reduction (the deferral), state tax, carryforwards beyond this year, and your full portfolio.
On the defaults above, the worked example returns $2,200. Harvesting $10,000 offsets roughly $2,200 of tax this year — but remember only $3,000 of a net loss can hit ordinary income; the rest must offset gains or carry forward.
04 It's deferral, not free money
Here's the part the headlines skip. When you harvest and reinvest, your replacement lot has a lower cost basis than the position you sold. That means a larger taxable gain when you eventually sell the replacement — so the tax you "saved" largely comes back later. Tax-loss harvesting defers tax; it doesn't make it disappear.
The benefit that does survive is twofold. First, the time value of money: paying less tax now and more later is worth something because you keep more invested in between. Second, and bigger, is rate arbitrage: a harvested loss can offset ordinary income taxed up to 37%, while the gain you pay later is typically long-term capital gain taxed at 0%, 15%, or 20%. Converting a 37%-rate offset into a future 15–20% bill is a genuine, durable win — the deferral is just the bonus.
If you hold the replacement to death, the basis steps up for your heirs and the deferred gain can vanish entirely. That turns the deferral into permanent savings — one reason harvesting fits naturally into a long-term, hold-forever portfolio.
Source: IRS — Publication 550, Investment Income and Expenses
05 When it's worth it (and when it isn't)
Harvesting only applies to taxable accounts. Losses inside a 401(k), traditional IRA, or Roth IRA are never deductible because nothing inside them is taxed annually — so don't even think about it there. Within a taxable account, it's most valuable when you have real gains to offset, you're in a high ordinary bracket, and the market has handed you a dip to work with.
| Situation | Worth harvesting? |
|---|---|
| Big realized gains this year, in a high bracket | Yes — offsets gains and shifts rate |
| Market dip, long-term taxable holdings | Yes — bank the loss, carry it forward |
| Loss only in your 401(k) or IRA | No — not deductible |
| Tiny loss with trading costs or a wash-sale risk | Usually not — don't distort the portfolio |
My rule: harvest when it's convenient and meaningful, not as a quarterly obsession. Never sell a position you want to keep just to book a small loss, and never buy a worse fund just to dodge a wash sale. The investment decision comes first; the tax benefit is a rebate on a portfolio you'd hold anyway.
The full decision is in Withdrawal Sequencing.
Tax-loss harvesting is real money, but it's oversold — most of what you "save" you pay back later through a lower basis. The durable win for me is the rate arbitrage: I offset ordinary income at 37% now and expect to pay 15–20% long-term gains later, plus the deferral keeps more money compounding in between. So I harvest when a dip hands me a clean loss and I have gains to soak it up. What I won't do is trigger a wash sale by rebuying too fast, or distort my allocation chasing a deduction. Keep the portfolio you want; take the tax benefit when it falls in your lap.
FAQ
What is tax-loss harvesting?
Selling an investment at a loss in a taxable account to realize a capital loss. The loss offsets capital gains dollar-for-dollar, and any net loss beyond gains offsets up to $3,000 of ordinary income per year ($1,500 if married filing separately). Anything left over carries forward indefinitely.
What 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 and adds it to the basis of the new lot. It applies across all your accounts, including IRAs and a spouse's. Buy a similar-but-not-identical fund to stay invested without triggering it.
Does tax-loss harvesting eliminate tax or just defer it?
Mostly it defers. Reinvesting at a lower basis means a larger gain later, so the tax comes back when you sell. The durable benefit is the time value of the deferral plus rate arbitrage — offsetting ordinary income taxed up to 37% now and paying long-term capital gains rates up to 20% later.
Can I harvest losses in my 401(k) or IRA?
No. Tax-loss harvesting only applies to taxable brokerage accounts. Gains and losses inside 401(k)s, traditional IRAs, and Roth IRAs are not taxed annually, so there is no loss to deduct.
Sources
Regulator references
- IRS — Topic no. 409, Capital gains and losses · Internal Revenue Service · 2025 · loss netting order and the $3,000 ordinary-income limitTax Topic 409: capital gains and losses, the holding period, and the rate categories.Last verified: 2026-06-21
- IRS — Publication 550, Investment Income and Expenses · Internal Revenue Service · 2025 · capital loss carryforwards and basisPublication 550: how investment income and expenses are reported, including the wash-sale rule.Last verified: 2026-06-21
- IRS — Wash sales (Publication 550) · Internal Revenue Service · 2025 · 30-day wash-sale rule and disallowed loss basis adjustmentPublication 550: how investment income and expenses are reported, including the wash-sale rule.Last verified: 2026-06-21
Calculator unit tests · the assertions this page's worked example is checked against, and their last result
Changelog
- 2026-06-21 — initial publish (new format)
Model this trade-off against your actual numbers
See how harvesting losses changes your after-tax projection — month by month to age 90.
Join the Waitlist
Jordan Reeves
Founder of Talk Through Wealth. A software engineer for over a decade before turning to retirement planning, Jordan built the projection engine after watching family members get fragmented, country-by-country advice that never reconciled. He writes about retirement the way the engine computes it: month-by-month, lifetime-long, and skeptical of any rule of thumb that hasn't been run through the math.