Nobody likes losing money on an investment. But here's the thing: when you sell an investment at a loss, the tax code actually gives you a chance to turn that disappointment into something useful. You can use those losses to reduce the taxes you owe on your gains鈥攐r even on your regular income. That's the idea behind tax loss harvesting. It won't make a bad investment good, but it can soften the blow and keep more money in your pocket.
What Is Tax Loss Harvesting?
Tax loss harvesting is the practice of selling an investment that has gone down in value to realize a capital loss. That loss can then offset capital gains you have from other investments. If your losses exceed your gains, you can even deduct up to $3,000 per year against your ordinary income (like your salary or freelance earnings). Any leftover losses roll over to future tax years.
The key word here is "realize." As long as you hold an investment, its loss is only on paper 鈥?a "paper loss," also called an unrealized loss. Once you sell, that loss becomes "realized," and the IRS lets you use it.
How Tax Loss Harvesting Works
Here's the simple mechanism: you sell a losing investment, capture the loss, and then 鈥?if you still want exposure to that investment 鈥?you buy a similar (but not "substantially identical") investment to replace it. This keeps your portfolio roughly the same while locking in a tax benefit.
The trick is avoiding the wash sale rule. If you buy the same or a "substantially identical" investment within 30 days before or after the sale, the IRS disallows the loss. You can't claim it. So you need to buy something similar but different 鈥?for example, if you sell a total stock market fund, you might buy an S&P 500 fund instead.
Let's break down the math with a simple example:
- You bought 100 shares of Fund A at $50 per share = $5,000 total.
- The price drops to $40 per share. Your position is now worth $4,000.
- You sell all 100 shares. You realize a loss of $1,000.
- You immediately buy 100 shares of Fund B (similar but not identical) for $4,000.
Now you have a realized loss of $1,000. If you also sold a winner that year for a $1,000 gain, those two cancel out. You pay zero tax on that gain. If you had no gains, you can deduct $1,000 from your ordinary income, saving you $220 in taxes if you're in the 22% bracket.
Real Examples With Numbers
Let's walk through a few scenarios so you can see exactly how this plays out.
Scenario 1: You Have Gains to Offset
Say you sold some stock this year for a $5,000 profit. That's a long-term capital gain. Normally, you'd owe 15% tax on that gain (assuming you're in the middle bracket). That's $750 in tax. But you also have a losing position 鈥?you bought a tech fund for $10,000, and now it's worth $7,000. You sell it.
Your math:
Realized capital gain: $5,000
Realized capital loss: $3,000
Net capital gain: $2,000
Tax owed (15%): $300 instead of $750. You saved $450.
Scenario 2: Losses Exceed Gains
Same situation, but this time you have a $6,000 loss on that fund.
Your math:
Gain: $5,000
Loss: $6,000
Net: $1,000 loss after offsetting the gain
You can deduct $1,000 from your ordinary income.
If you're in the 24% bracket, that saves you another $240.
The remaining $2,000 loss? It carries forward to next year.
Scenario 3: No Gains at All
You had no capital gains this year, but you realized a $5,000 loss. You can deduct up to $3,000 against your ordinary income this year. The remaining $2,000 carries forward to next year.
In the 22% tax bracket, that $3,000 deduction saves you $660 this year alone.
Pros and Cons
| Pros | Cons |
|---|---|
| Reduces your tax bill 鈥?directly offsets gains and ordinary income. | Wash sale rule 鈥?you can't buy the same investment back within 30 days, or the loss is disallowed. |
| Losses carry forward 鈥?unused losses don't expire; you can use them in future years. | Portfolio tracking becomes messier 鈥?you may end up with lots of small lots and different funds. |
| Works in any market 鈥?if you have losses, you can harvest them anytime. | High transaction costs 鈥?if you pay commissions or have high bid-ask spreads, the cost might outweigh the benefit. |
| No limit on amount of losses 鈥?you can offset unlimited gains, and deduct $3,000 per year against income. | Lower cost basis 鈥?you replace a high-cost investment with a lower-cost one, which may mean bigger gains later. |
That last point is worth repeating. If you sell a losing position at $40 and buy a similar one at $40, your new cost basis is $40. If the market recovers and you later sell at $60, you'll have a $20 gain per share. You deferred the tax, but you didn't eliminate it 鈥?unless you hold the new position until death (when heirs get a step-up in basis) or donate it.
Common Mistakes People Make
I see the same errors over and over. Avoid these and you'll be ahead of most investors.
- Triggering a wash sale without realizing it. If you sell a fund and buy the exact same fund within 30 days 鈥?even in a retirement account 鈥?the loss disappears. Double check your trades.
- Harvesting losses when you're in a low tax bracket. If you're in the 0% long-term capital gains bracket, you might be better off not harvesting. The loss could be more valuable in a future year when you have gains or higher income.
- Forgetting about state taxes. Some states don't allow the $3,000 deduction against ordinary income, and others have different rules. Know your state's treatment.
- Letting the tax tail wag the investment dog. Don't sell a good investment just to harvest a loss, especially if you believe it will rebound. Tax loss harvesting is a side benefit, not a reason to change your strategy.
- Not tracking carried-over losses. The IRS doesn't automatically tell you how much you have left. Keep a running tally, or use your tax software to track it.
Tools That Make This Easier
Doing the math by hand is possible, but it's tedious 鈥?especially if you have multiple accounts and lots of trades. A few calculators on ToolBoxHub can do the heavy lifting for you.
If you're trying to figure out how much tax you'll save from a specific loss, use the Capital Gains Calculator. You can input your purchase price, sale price, and holding period, and it will tell you your gain or loss and the estimated tax impact. This is your go-to tool when you're deciding whether to harvest a specific position.
To see how tax loss harvesting fits into your bigger financial picture, the Investment Calculator lets you project your portfolio growth over time, and you can adjust for the tax savings you're getting. For example, if you save $660 this year from a $3,000 deduction, you can add that back into your investments and see how it compounds over 10 or 20 years.
And don't forget the Income Tax Calculator. Use it to estimate your marginal tax rate for the year. That's the number you multiply your deduction by to figure out your real savings. If you're on the edge of a tax bracket, knowing your exact rate is critical before you execute any trades.
Frequently Asked Questions
Can I harvest losses in my 401(k) or IRA?
No. Losses inside tax-advantaged accounts like 401(k)s, traditional IRAs, and Roth IRAs don't count for tax loss harvesting. You only get the benefit when you sell investments in a taxable brokerage account.
What counts as a "substantially identical" investment?
The IRS is intentionally vague here, but the general rule is: the two investments must not be so similar that they are essentially the same. Selling one S&P 500 index fund and buying a different S&P 500 index fund likely triggers a wash sale. Selling an S&P 500 fund and buying a total stock market fund is generally safe. Selling an Apple stock and buying a Microsoft stock is fine.
Should I harvest losses in December, or can I do it anytime?
You can do it any day of the year. Many people wait until December because they know their annual gains by then, but market drops happen all year. If you see a big loss in March, there's no reason to wait. The earlier you harvest, the sooner you can use the loss.
What happens if I accidentally trigger a wash sale?
The loss isn't gone forever 鈥?it's just disallowed for now. The disallowed loss gets added to the cost basis of the replacement shares. So you'll get the benefit when you eventually sell those replacement shares (as long as you don't create another wash sale). It's a deferral, not a permanent loss of the benefit.
Is tax loss harvesting worth it for small amounts?
That depends on your time and transaction costs. If you can save $50 or $100 in taxes with a few clicks, that's worth it for most people. If you have to pay a broker fee or spend 30 minutes tracking it, maybe not. For small amounts, consider batching your harvests 鈥?do them all at once toward the end of the year.