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Insight · Tax-Loss Harvesting
Tax-Loss Harvesting: How Much Can It Actually Save You?
If your taxable brokerage account has any investments sitting at a loss right now, there may be a way to turn that disappointment into a genuine tax break before December 31. Tax-loss harvesting is one of the most widely discussed year-end tax moves available to investors, yet many people either overlook it or misunderstand how it actually works. This guide breaks down the mechanics, the limits, and the real dollar math so you can have a more informed conversation with your tax adviser.
Your Portfolio Is Down on Some Positions. That Might Actually Be Good News.
Nobody enjoys looking at a red number in their brokerage account. But here is the thing: in a taxable investment account, a position sitting at a loss is not purely bad news. It is a potential tax asset, and the window to use it for the current tax year closes on December 31.
Tax-loss harvesting is the practice of intentionally selling investments at a loss to generate a tax deduction that can work in two ways. First, those realized losses can offset capital gains you have taken elsewhere in your portfolio this year. Second, if your losses exceed your gains, up to $3,000 of the remaining loss can offset ordinary income, such as wages or Social Security. Anything beyond that carries forward into future tax years with no expiration date under current IRS rules.
This is not a fringe strategy. It is a straightforward part of the tax code that many investors with taxable brokerage accounts explore each fall. The catch is that the rules matter enormously, and one common mistake, the wash-sale violation, can wipe out the benefit entirely. Let us walk through how it all works, what the numbers look like in practice, and what pitfalls to watch for.
How Tax-Loss Harvesting Works: The Core Mechanics
When you sell an investment in a taxable brokerage account for more than you paid, you have a capital gain. The IRS taxes that gain, and the rate depends on how long you held the asset and your total income. When you sell an investment for less than you paid, you have a capital loss. The tax code allows you to use that loss to offset gains, and in limited amounts, to offset ordinary income.
Here is how the offsetting works step by step:
Short-term losses first offset short-term gains. Short-term gains (on assets held one year or less) are taxed as ordinary income, so this pairing is especially valuable.
Long-term losses first offset long-term gains. Long-term gains (assets held more than one year) are taxed at the preferential 0%, 15%, or 20% rates.
Any remaining net loss offsets the other category. If you have leftover short-term losses after wiping out short-term gains, they can then offset long-term gains, and vice versa.
Net losses up to $3,000 offset ordinary income. If total realized losses still exceed total realized gains after all the above netting, up to $3,000 of that net loss can reduce your ordinary taxable income for the year. The $3,000 limit applies to individuals and married couples filing jointly; it is $1,500 for married filing separately (IRS Publication 550).
Excess losses carry forward. Any net capital loss above $3,000 does not disappear. It carries forward to the next tax year and can be used in the same way, indefinitely, until it is fully used.
It is worth noting that this strategy only applies to taxable brokerage accounts. Losses inside a 401(k), IRA, or Roth IRA cannot be harvested because those accounts are already tax-advantaged and gains inside them are not taxed in the same way.
The Numbers: What Can Tax-Loss Harvesting Actually Save You?
The savings depend on two things: the size of the loss and your tax bracket. Let us look at three illustrative, hypothetical examples to make this concrete. These are fictional scenarios for educational purposes only and do not represent any specific individual's situation.
Hypothetical Example 1: Offsetting Long-Term Capital Gains
Imagine a hypothetical investor who sold a stock fund earlier in the year and realized a $10,000 long-term capital gain. Later in the year, she notices another position is down $8,000 from her cost basis. If she sells that losing position before year-end, she generates an $8,000 realized loss that directly offsets $8,000 of her $10,000 gain. She is now only taxed on $2,000 of long-term gain instead of $10,000.
In the 15% long-term capital gains bracket, the tax on $10,000 would have been $1,500. After harvesting, the tax on $2,000 is $300. Estimated savings: $1,200.
In the 20% bracket, the original tax would have been $2,000. After harvesting, it is $400. Estimated savings: $1,600.
Hypothetical Example 2: No Gains to Offset, Using the $3,000 Ordinary Income Deduction
Consider a hypothetical retiree who has no realized gains this year but has a position down $15,000. If he sells, the first $3,000 of that loss can offset ordinary income. If his marginal ordinary income tax rate is 22%, that $3,000 deduction saves him $660 in federal taxes this year. The remaining $12,000 carries forward to future years, where it can offset gains or ordinary income again at up to $3,000 per year.
Hypothetical Example 3: Combining Both Effects
A hypothetical investor in the 15% long-term capital gains bracket and the 22% ordinary income bracket has $5,000 in realized long-term gains and $9,000 in realized losses. After netting, she has a $4,000 net capital loss. The first $5,000 of losses offset the $5,000 of gains entirely (saving $750 in capital gains taxes at 15%). Of the remaining $4,000 net loss, $3,000 offsets ordinary income, saving an additional $660 at the 22% rate. The last $1,000 carries forward. Total estimated first-year savings: approximately $1,410.
These examples illustrate why the strategy is often discussed in the context of estimating your real retirement tax bill, since gains in taxable accounts can meaningfully affect your annual tax situation.
Note: These figures are illustrative estimates for educational purposes. Individual results will vary based on specific cost basis, holding periods, state taxes, the Net Investment Income Tax (which applies a 3.8% surcharge to investment income above certain thresholds for higher earners), and other factors. A tax professional can calculate your actual figures.
The Wash-Sale Rule: The Trap That Can Erase Your Benefit
This is where many investors stumble, and it is the most important rule to understand before attempting any tax-loss harvesting.
The wash-sale rule, codified in IRS Publication 550 and Section 1091 of the Internal Revenue Code, states that if you sell a security at a loss and then buy a substantially identical security within 30 days before or after that sale, the loss is disallowed for tax purposes. The disallowed loss is not gone forever; it gets added to the cost basis of the replacement security. But it does eliminate the immediate tax benefit, which is the whole point of the exercise.
The 30-day window runs in both directions: 30 days before the sale and 30 days after. This is often called the 61-day window (the day of the sale plus 30 days on each side).
What counts as substantially identical? The IRS does not provide a definitive list, but the general principle is:
Selling a stock and buying the same stock back: clearly a wash sale.
Selling a mutual fund and buying the same fund from the same fund family tracking the same index: likely a wash sale.
Selling an S&P 500 index fund from one provider and buying a different S&P 500 index fund from another provider: this is a debated gray area. Many tax professionals treat near-identical index funds as potentially triggering the rule, while others do not. The IRS has not issued definitive guidance on all ETF-to-ETF switches.
Selling an S&P 500 fund and buying a total market fund or a different broad index: generally not considered substantially identical, though opinions vary and the IRS has not ruled definitively on all scenarios.
One more wash-sale complication to be aware of: the rule also applies across accounts. If you sell a stock at a loss in your taxable account and your spouse, or an IRA you control, buys the same security within the wash-sale window, the loss can still be disallowed. This cross-account issue catches investors off guard more often than the basic rule does.
Because the line between a legitimate tax-loss harvest and a wash sale can be blurry, working with a tax professional before executing trades is genuinely valuable here.
Common Mistakes to Avoid
Beyond the wash-sale violation, several other mistakes can reduce or eliminate the value of tax-loss harvesting:
Harvesting losses in a tax-deferred or tax-exempt account. As noted, this strategy only works in taxable brokerage accounts. Losses inside a traditional IRA or 401(k) do not generate a deductible loss under current tax law.
Ignoring the holding period. If you sell an investment you have held for exactly one year and one day, it qualifies as a long-term loss. If you sell after eleven months, it is short-term. This matters because short-term losses are most valuable when offsetting short-term gains, which are taxed at ordinary income rates. Mismatching loss types with gain types can reduce effectiveness.
Forgetting state taxes. Many states follow federal capital gains rules, but not all. Some states tax capital gains as ordinary income regardless of holding period. Your state tax situation affects the total savings calculation.
Harvesting without a reinvestment plan. If you sell an investment and sit in cash for 31 days to avoid the wash-sale window, you may miss market movements during that period. Having a comparable (but not substantially identical) replacement in mind before selling is a consideration many investors weigh carefully.
Ignoring transaction costs and bid-ask spreads. For smaller loss amounts, trading costs could offset a portion of the tax savings, particularly with less liquid securities.
Assuming the carryforward is unlimited in time but unlimited in amount per year. The carryforward carries forward the full amount, but only $3,000 per year can offset ordinary income. Offsetting capital gains from carryforwards is not subject to the $3,000 cap and can offset gains dollar for dollar.
Understanding these nuances also matters in the broader context of tax planning across different account types, where the interaction of taxable and tax-advantaged accounts can create both opportunities and surprises.
Year-End Timing: What to Review Before December 31
The calendar matters for this strategy. Realized losses must occur in the same tax year as the gains they are meant to offset, and trades in taxable accounts must settle before year-end. For most US equities, settlement currently occurs on the next business day after the trade date (T+1), so waiting until December 31 to trade is cutting it very close. Many investors and advisers discuss completing any tax-loss harvesting decisions before mid-December to allow for settlement and to avoid last-minute market chaos.
A general review at year-end might involve looking at:
Which positions in your taxable account are currently showing unrealized losses.
What realized gains you have already taken this year (your brokerage's tax center or year-to-date gain/loss report is a common starting point for this review).
Whether you have any capital loss carryforwards from prior years that are already working in your favor, which might reduce how much additional harvesting is needed.
The 30-day wash-sale window relative to any recent purchases of the same securities.
The IRS provides detailed guidance on capital gains and losses in IRS Publication 550 (Investment Income and Expenses) and Schedule D instructions, both of which are available at irs.gov. These are useful reference documents when reviewing your situation with a tax professional.
It is also worth connecting this kind of year-end tax review to your broader financial picture. For example, understanding how investment income interacts with your retirement projections is one reason many people find tools that model the tax math around Roth conversions alongside taxable account planning to be useful.
Frequently Asked Questions
Can I use tax-loss harvesting inside my IRA or 401(k)?
No. Tax-loss harvesting only applies to taxable brokerage accounts. Inside a traditional IRA or 401(k), investment gains are tax-deferred and you do not pay capital gains tax on transactions within the account. Inside a Roth IRA, qualified withdrawals are tax-free. Because gains in these accounts are not currently taxed, there is no mechanism under current IRS rules to claim a deductible loss from trades made inside them. The strategy is exclusively a taxable account tool.
Does the $3,000 ordinary income deduction reset every year?
Yes. Each tax year, up to $3,000 of net capital losses (above any capital gains you have offset) can be deducted against ordinary income. If your total net capital loss exceeds $3,000, the excess carries forward to the following year. In that next year, the carryforward loss first offsets any new capital gains, and if losses still exceed gains, up to another $3,000 can offset ordinary income again. This continues each year until the carryforward balance is fully used. The carryforward does not expire under current tax law.
Does tax-loss harvesting permanently save taxes, or does it just defer them?
This is an important nuance. In many cases, tax-loss harvesting is a deferral strategy rather than a permanent elimination of taxes. When you sell at a loss and buy a similar (but not identical) replacement, your cost basis in the new position is lower than it would have been if you had held the original. When you eventually sell the replacement position at a gain, you may owe more in taxes at that point. The value of the strategy comes from the time value of money: paying less tax now and more tax later, potentially at a lower rate, is generally better than paying more tax now. In some cases, such as holding the replacement until death and passing it to heirs who receive a stepped-up cost basis, the deferred tax may never come due under current law. A tax professional can help model the long-term picture for your specific situation.
A note on this content: This article is general educational information about how tax-loss harvesting works under current US tax law. It is not personalized tax advice, investment advice, or a recommendation to buy or sell any security. Tax outcomes vary significantly based on individual circumstances including income, filing status, state of residence, cost basis, holding periods, and other factors. Before making any decisions about tax-loss harvesting or any other tax strategy, consult a qualified tax professional (such as a CPA or enrolled agent) and a registered financial adviser who can evaluate your specific situation. IRS rules can change, and this article reflects general principles as of the time of writing.
If you are thinking about how your taxable accounts and retirement accounts fit together into a complete picture, exploring the key numbers that define your retirement readiness can be a helpful place to see how all the pieces connect.
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