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Tax-Loss Harvesting Explained & When It Makes Sense

Tax-Loss Harvesting Explained & When It Makes Sense

October 21, 2026

With roughly ten weeks left in 2026, it is a good time to look at your taxable investment accounts for something most investors overlook: losses. An investment that has dropped below what you paid is frustrating, but it can also be useful. Selling it at a loss can reduce the tax you owe on gains and, in some cases, on ordinary income.

That strategy is called tax-loss harvesting. This post covers what it is, where it works, and when it makes sense, so you can have a better conversation with your advisor and tax professional before year-end.

What tax-loss harvesting is

Tax-loss harvesting means selling an investment that is worth less than you paid for it, recording a capital loss, and using that loss to offset taxes. You then typically reinvest the proceeds in something similar, so your portfolio stays on course while you capture the tax benefit.

The loss only counts for tax purposes once you sell. Until then it is a paper loss. The losses you harvest can offset capital gains you realized from other sales, as well as capital gain distributions paid by funds you own. If your losses exceed your gains, a limited amount can offset ordinary income.

Which accounts it works in

Tax-loss harvesting only works in taxable accounts, such as individual accounts, joint accounts, and most trust accounts. In these accounts, the gains and losses from your sales show up on your tax return every year.

It does not work in IRAs, Roth IRAs, 401(k)s, or similar retirement accounts. The IRS notes that the investment income and capital gain rules in Publication 550 do not apply to investments held in those accounts. Gains and losses inside them are not reported each year, so a loss there creates no deduction. Tax on a traditional IRA or 401(k) is generally deferred until you take a distribution, and qualified Roth distributions are not taxed.

That difference is why it matters which account holds which investment. A decline in a retirement account is a market loss, but not a tax opportunity.

How the tax math works

Capital gains and losses are sorted into short-term (held one year or less) and long-term (held more than one year). Losses first offset gains of the same type, and then any remainder offsets the other type. This matters because short-term gains are taxed as ordinary income, while long-term gains are taxed at 0%, 15%, or 20%, depending on your taxable income.

If your losses exceed your gains for the year, you can use up to $3,000 of the excess ($1,500 if married filing separately) to reduce other income. Anything beyond that carries forward to later years, so a large loss is not wasted.

Here are two hypothetical examples, assuming the 15% long-term rate applies:

Scenario

Gains realized

Losses harvested

Result

A

$12,000

$9,000

Taxable gain falls to $3,000, cutting federal tax by about $1,350

B

$4,000

$10,000

$6,000 net loss: $3,000 reduces other income now, $3,000 carries forward

These are simplified illustrations. Your actual result depends on your income, filing status, and which lots you sell.

The wash sale rule

The biggest trap in tax-loss harvesting is the wash sale rule. Under IRS Publication 550, a loss is disallowed if you sell at a loss and, within 30 days before or after the sale, buy the same or a "substantially identical" investment. That creates a 61-day window around the sale date.

A few details catch people off guard:

  • It applies across accounts. Buying the replacement in your IRA or Roth IRA can trigger it, and so can a purchase by your spouse, per Fidelity's summary of the IRS rules.
  • Automatic purchases count. Dividend reinvestment can buy shares inside the window without you placing a trade.
  • The loss is deferred, not always gone. When a loss is disallowed in a taxable account, it is generally added to the cost basis of the replacement shares, and the holding period carries over. You get the benefit later, when you sell the replacement. A loss disallowed because of a purchase in an IRA, however, may be lost for good.

The usual workaround is to reinvest in a similar but not substantially identical holding, such as a different fund tracking a different index, or to wait 31 days. What counts as substantially identical is not always clear, so confirm the details with your advisor or tax professional before you trade.

When it makes sense

Harvesting tends to be most useful when one or more of these apply:

  • You have realized gains to offset. Selling a rental property, a business interest, or a concentrated stock position can create a large gain. Losses elsewhere in your portfolio can absorb part of it.
  • You expect capital gain distributions. Many mutual funds pay out gains in the fall and December, and you owe tax on them even if the fund's price fell. Harvested losses can offset those payouts.
  • You are in a higher tax bracket. The higher your rate on gains, the more each dollar of loss is worth.
  • You hold positions that have fallen. That can include stocks, funds, and bond funds that lost value when rates rose, as long as you still want the exposure and can replace it with something similar.
  • You are rebalancing anyway. If you already plan to trim or change a holding, selling the lots with the biggest losses first can turn a routine trade into a tax benefit.

Timing matters too. Because of the 30-day wash sale window, waiting until the last week of December leaves little room to plan, so it helps to review positions earlier.

When it may not help

Tax-loss harvesting is not free money, and sometimes it adds little or works against you:

  • It defers tax more than it eliminates it. The replacement investment has a lower cost basis, so a larger gain may be waiting when you eventually sell. The benefit is the value of paying later, and sometimes at a lower rate.
  • You are in the 0% long-term capital gains bracket. If your taxable income is low enough that long-term gains are not taxed, a loss may save you nothing now. In that case, realizing gains instead can be the smarter move. The IRS publishes the bracket thresholds, and they adjust each year.
  • The investment is in a retirement account. There is nothing to harvest, as covered above.
  • The loss is small. Trading costs, bid-ask spreads, and the time to manage the trade can outweigh a modest tax saving.
  • The replacement changes your risk. Swapping into something that behaves differently can leave you with a portfolio you did not intend. The tax tail should not wag the investment dog.
  • You have little unrealized loss to work with. Assets received through inheritance generally take a basis equal to their value at the owner's death, which can leave few gains or losses to harvest early on.

State taxes, your other income, and your longer-term plans can all change the math, which is why this decision is best made with your full picture in view.

Why it matters more in retirement

For retirees and pre-retirees, capital gains do more than add to your tax bill. They raise your income, which can ripple into other parts of your plan:

  • Social Security taxation. Higher income can increase how much of your Social Security benefit is taxable.
  • Medicare premiums. Income above certain thresholds triggers higher Part B and Part D premiums, known as IRMAA. The surcharge is based on income from two years earlier, so a large gain this year can raise premiums later.
  • Net investment income tax. This is a 3.8% tax on investment income once your modified adjusted gross income passes $200,000 for single filers or $250,000 for married couples filing jointly. Those thresholds are not indexed for inflation.

Because harvested losses reduce your net gains, they can help keep income below some of these thresholds. That is why harvesting is often worth considering in a year when you plan to sell appreciated assets. Keep in mind that losses mainly offset gains, and only $3,000 a year can offset other income, so they will not shelter a large IRA distribution or Roth conversion.

Questions to ask before year-end

Tax-loss harvesting works best as part of a plan, not as a last-minute trade. Before the year closes, consider:

  • Which of my taxable holdings are below what I paid, and which lots have the largest losses?
  • Have I realized, or do I expect to realize, gains this year from a sale or a fund distribution?
  • Could any planned purchase, including automatic reinvestment, trigger a wash sale?
  • How would more or less income affect my Social Security taxes and Medicare premiums?

If you would like to walk through these questions, schedule a conversation and we can review your taxable accounts alongside your tax professional, well before the year-end rush.

Disclosures (replace with your firm's approved language before publishing): Tax laws and regulations are complex and subject to change. This content is for educational purposes only and is not individualized investment, tax, or legal advice. Consult a qualified tax professional about your situation. Examples are hypothetical and do not represent actual results. Investing involves risk, including possible loss of principal, and past performance is no guarantee of future results.

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