Year-End Tax-Loss Harvesting: A Beginner’s Guide for 2026

As the year winds down, you’ll hear the phrase “tax-loss harvesting.” It sounds technical, but the idea is simple: if some of your investments are worth less than you paid, selling them can create a loss that lowers your tax bill. Here’s how it works, the rules that trip people up, and a checklist to use before December 31.

First, who this applies to

Tax-loss harvesting only matters in taxable accounts, like a regular brokerage account. Gains and losses inside IRAs, 401(k)s, and HSAs aren’t taxed year to year, so there’s nothing to harvest there.

The basics: capital gains and losses

When you sell an investment:
– Sell for more than your cost basis (generally what you paid) and you have a capital gain.
– Sell for less and you have a capital loss.

The IRS sorts these by how long you held the investment:
– Short-term: held one year or less. Net short-term gains are taxed as ordinary income.
– Long-term: held more than one year. Net long-term gains usually get lower tax rates, and some people pay 0%.

How harvesting lowers your taxes

1. Losses offset gains. If you sold something at a gain this year, a realized loss can cancel out some or all of it.
2. Extra losses offset regular income, up to a limit. If your losses exceed your gains, the IRS lets you deduct the lesser of $3,000 ($1,500 if married filing separately) or your total net loss against other income.
3. Leftover losses carry forward. Anything above that limit can be carried to future years.

A simple example (hypothetical numbers)

Say that this year you:
– Sold Fund A for a $4,000 gain
– Still hold Fund B, which is down $6,000 from what you paid

If you sell Fund B, the $6,000 loss first wipes out the $4,000 gain. The remaining $2,000 can reduce your ordinary income, since it’s under the $3,000 limit. You’d owe no tax on the Fund A gain, and you’d lower your taxable income too.

The rule that trips people up: wash sales

You can’t sell at a loss and immediately buy the same thing back. A wash sale happens when you sell at a loss and, within 30 days before or after the sale, you:
– Buy substantially identical stock or securities,
– Acquire them in a fully taxable trade,
– Acquire a contract or option to buy them, or
– Buy them in your IRA or Roth IRA.

It also counts if your spouse or a corporation you control buys substantially identical stock.

If it’s a wash sale, you can’t deduct the loss now. Generally, the disallowed loss is added to the cost basis of the new shares, which postpones the deduction. The big exception: when the repurchase happens in your IRA, the IRS’s list doesn’t include that basis adjustment, so the loss may be lost for good.

What counts as “substantially identical”? The IRS says it depends on the facts and circumstances. Shares of one company usually aren’t substantially identical to shares of a different company. Swapping one fund for another that tracks the exact same index is a gray area, so many people pick a fund with a meaningfully different index or ask a tax professional.

Watch out for automatic purchases. Dividend reinvestment or recurring buys in the same fund within the 30-day window can trigger a wash sale without you noticing.

Year-end checklist

1. Review your taxable accounts for positions worth less than your cost basis.
2. Total your realized gains for the year, including fund distributions.
3. Decide what to sell. Don’t sell something you truly want to own just for a tax break.
4. Plan your replacement. Either wait more than 30 days or choose an investment that isn’t substantially identical.
5. Pause automatic buys of the same holding in all your accounts, including your spouse’s and your IRAs.
6. Trade before the year ends. Check your broker’s deadlines for trades to settle in the tax year you want.
7. Keep records and check your Form 1099-B when it arrives.

When harvesting may not be worth it

• Your income is low and your long-term gains may already be taxed at 0%.
• The loss is tiny compared with trading costs and hassle.
• It would knock your portfolio off its target mix.
• You’d be tempted to time the market while you’re out of the investment.

Keep the big picture

Tax savings are nice, but they’re a bonus, not a strategy. A diversified, low-cost portfolio you can stick with matters far more; see Investing 101 – Creating a Diversified Portfolio With ETFs. Using tax-advantaged accounts first, like a Roth IRA or the other accounts in Investing Outside of a 401k, can reduce how much you need to think about any of this. Need a refresher on terms like “cost basis”? See Investing Vocabulary – 45 Terms You Should Know.

One more tip: mind short vs. long

Short-term losses first offset short-term gains, and long-term losses first offset long-term gains, before either crosses over. Since short-term gains are taxed at ordinary income rates, offsetting them can be especially valuable. Your tax software or Schedule D handles the math.

The bottom line

Tax-loss harvesting turns investment losses in taxable accounts into tax savings: offset gains, deduct up to $3,000 against income, and carry the rest forward. Just respect the 30-day wash sale rule, including purchases in IRAs and your spouse’s accounts, and don’t let the tax tail wag the investment dog. For anything complex, talk with a tax professional.