Tax Loss Harvesting Guide

Tax loss harvesting is a strategy that may help investors reduce their current tax liability by selling investments that have declined in value. By strategically realizing losses, taxpayers can generally offset capital gains and, in some cases, reduce ordinary income. While this approach is widely used by individual investors and financial advisors alike, it involves important rules, limitations, and potential pitfalls that merit careful consideration. This guide covers the mechanics, benefits, risks, and practical applications of tax loss harvesting for the 2024 and 2025 tax years.

Key Takeaways

• Tax loss harvesting involves selling investments at a loss to offset realized capital gains, potentially lowering your tax bill in a given year.
• The IRS wash sale rule (IRC Section 1091) generally prohibits claiming a loss if you purchase a “substantially identical” security within 30 days before or after the sale.
• If capital losses exceed capital gains in a given year, taxpayers may typically deduct up to $3,000 ($1,500 if married filing separately) against ordinary income, with excess losses carried forward to future years (IRS Publication 550).
• While tax loss harvesting can defer and reduce taxes, it is not a risk-free strategy and may result in lower cost bases, unexpected wash sale violations, and complications during an audit.
• This strategy is generally most effective for taxpayers in higher tax brackets who have significant realized capital gains in a given tax year.

How Tax Loss Harvesting Works

The Basic Mechanics

At its core, tax loss harvesting involves three steps: identifying investments in your taxable accounts that have unrealized losses, selling those investments to “realize” the loss, and then using those realized losses to offset capital gains. If losses exceed gains, the remaining loss may typically be used to offset up to $3,000 of ordinary income per year ($1,500 for married individuals filing separately), as outlined in IRS Publication 550.

Consider a practical example: Suppose an investor purchased 100 shares of a stock for $10,000 in early 2024. By October 2024, the value has declined to $7,000. If the investor sells all 100 shares, they realize a $3,000 capital loss. If that same investor also sold another investment earlier in the year for a $5,000 capital gain, the $3,000 loss would offset a portion of that gain, meaning the investor would only owe capital gains tax on $2,000 of net gain.

Short-Term vs. Long-Term Losses

The tax benefit of harvested losses depends in part on whether the losses and gains are classified as short-term or long-term. Under IRS rules (Publication 544), assets held for one year or less generate short-term capital gains or losses, while those held for more than one year generate long-term capital gains or losses.

According to IRS netting rules, short-term losses are first applied against short-term gains, and long-term losses are first applied against long-term gains. If there is a net loss in either category, it may then be used to offset gains in the other category. This distinction matters because short-term capital gains are generally taxed at ordinary income rates (up to 37% for the 2024 tax year), while long-term capital gains are typically taxed at preferential rates of 0%, 15%, or 20%, depending on taxable income (IRS Revenue Procedure 2023-34 for 2024 rates).

Tax Rate Category	2024 Single Filer Threshold	2024 Married Filing Jointly Threshold
0% Long-Term Capital Gains	Up to $47,025	Up to $94,050
15% Long-Term Capital Gains	$47,026 to $518,900	$94,051 to $583,750
20% Long-Term Capital Gains	Over $518,900	Over $583,750

Because short-term gains are taxed at higher rates, harvesting short-term losses to offset short-term gains generally produces a larger immediate tax benefit than offsetting long-term gains. However, the netting order is dictated by IRS rules rather than taxpayer preference.

The Wash Sale Rule

Understanding the 61-Day Window

The wash sale rule, codified in Internal Revenue Code Section 1091 and explained in IRS Publication 550, is the single most important constraint on tax loss harvesting. This rule generally disallows a capital loss deduction if the taxpayer purchases a “substantially identical” security within 30 days before or 30 days after the sale at a loss. This creates a 61-day window (30 days before, the day of sale, and 30 days after) during which purchasing the same or a substantially identical investment will trigger a wash sale.

When a wash sale occurs, the disallowed loss is not permanently lost. Instead, it is typically added to the cost basis of the replacement security, which may reduce the gain (or increase the loss) when that replacement security is eventually sold. The holding period of the original security is also generally tacked onto the holding period of the replacement.

What Qualifies as “Substantially Identical”

The IRS has not provided an exhaustive definition of “substantially identical,” which creates some ambiguity. In most cases, the following are considered substantially identical:

• Shares of the same stock or the same mutual fund
• Options or contracts to acquire substantially identical stock
• Shares repurchased in a dividend reinvestment plan (DRIP) within the wash sale window

The following are generally not considered substantially identical, though taxpayers may want to exercise caution:

• Shares of a different company in the same industry (e.g., selling one bank stock and buying a different bank stock)
• An index fund tracking a different index (e.g., selling an S&P 500 fund and purchasing a total stock market fund)
• An ETF versus a mutual fund that tracks different, though related, indices

It is important to note that the IRS could potentially challenge transactions where the replacement security is very similar, even if it is not technically the same security. This area involves judgment, and aggressive interpretations may carry audit risk.

Wash Sale Rule Across Accounts

A commonly overlooked aspect of the wash sale rule is that it applies across all of a taxpayer’s accounts, including IRAs and other tax-advantaged accounts. If an investor sells a stock at a loss in a taxable brokerage account and then purchases the same stock within 30 days in an IRA, the wash sale rule is generally triggered. In this specific scenario (involving an IRA purchase), the disallowed loss may be permanently lost because the basis adjustment cannot be applied to shares held in a tax-deferred account (IRS Publication 550). This is a particularly costly mistake.

Additionally, the wash sale rule typically applies to purchases made by a spouse in a joint or separate account, though the IRS guidance on this point is not entirely comprehensive. Coordinating transactions across spousal accounts is generally advisable.

Practical Tax Loss Harvesting Examples

Example 1: Offsetting Capital Gains

Maria, a single filer with $200,000 in taxable income for 2024, sold shares of a technology ETF in March 2024, realizing a long-term capital gain of $15,000. In November 2024, she reviews her portfolio and finds that shares of an international stock fund she purchased for $30,000 are now worth $20,000. She sells the international fund, realizing a $10,000 long-term capital loss.

After netting, Maria has a net long-term capital gain of $5,000 ($15,000 gain minus $10,000 loss). At her income level, this gain would typically be taxed at 15%, resulting in a tax liability of approximately $750 instead of the $2,250 she would have owed on the full $15,000 gain. To maintain her portfolio allocation, Maria purchases a different international fund that tracks a different index after the sale.

Example 2: Offsetting Ordinary Income

James, a married taxpayer filing jointly, has no capital gains in 2024 but realizes $8,000 in capital losses through tax loss harvesting. Under IRS rules, he may deduct $3,000 of those losses against his ordinary income on his 2024 return. The remaining $5,000 in losses carries forward to 2025 and beyond until fully utilized. If James is in the 32% tax bracket, the $3,000 deduction may reduce his 2024 tax liability by approximately $960.

Example 3: A Wash Sale Mistake

Lisa sells 200 shares of XYZ Corporation on December 10, 2024, at a loss of $4,000. On December 28, 2024, she buys 200 shares of XYZ Corporation because she believes the stock is poised to recover. Because the repurchase occurred within 30 days of the sale, the $4,000 loss is disallowed under the wash sale rule. The $4,000 is added to the cost basis of the new shares, and the holding period of the original shares carries over. Lisa does not receive any tax benefit in 2024 from this transaction.

Benefits and Limitations

Potential Benefits

• Tax deferral: By offsetting gains in the current year, investors may defer tax payments to future years, potentially allowing more capital to remain invested and compound.
• Ordinary income reduction: The $3,000 annual deduction against ordinary income (per IRS Publication 550) can provide ongoing tax benefits, especially when losses are substantial and carry forward for multiple years.
• Portfolio rebalancing opportunity: Tax loss harvesting can serve as a catalyst for rebalancing a portfolio, replacing underperforming investments with alternatives that may better align with investment goals.
• Estate planning considerations: If harvested losses create a lower cost basis that is never realized during the taxpayer’s lifetime, the step-up in basis at death (under IRC Section 1014) may effectively eliminate the deferred gain entirely.

Limitations and Risks

• Tax deferral, not elimination: In many cases, tax loss harvesting defers taxes rather than eliminating them. The replacement security typically has a lower cost basis, which may result in a larger taxable gain when that security is eventually sold.
• Transaction costs: Frequent buying and selling may generate brokerage fees, bid-ask spreads, and other transaction costs that could erode the tax benefit, though many brokerages now offer commission-free trading.
• Wash sale complexity: Managing the 61-day window across multiple accounts (including retirement accounts and spousal accounts) can be administratively burdensome and error-prone.
• Impact on asset allocation: Replacing a sold security with one that is different enough to avoid wash sale issues may introduce tracking error or change the risk profile of the portfolio.
• Net Investment Income Tax (NIIT): For high-income taxpayers, the 3.8% NIIT (IRC Section 1411) applies to net investment income above certain thresholds ($200,000 for single filers, $250,000 for married filing jointly in 2024). Tax loss harvesting may reduce exposure to this additional tax, but the interaction requires careful calculation.
• State tax considerations: Not all states conform to federal capital gains rules. Some states may have different treatment of capital losses or different carryforward rules, which could affect the overall benefit of the strategy.

Audit Risks and Compliance Considerations

Tax loss harvesting, when executed properly, is a legitimate and widely accepted tax planning strategy. However, certain practices may attract IRS scrutiny:

• Failure to report wash sales: Brokerages are required to report wash sales on Form 1099-B, but they typically only track wash sales within a single account. Wash sales across multiple accounts or brokerages may not be automatically reported, and the taxpayer is responsible for proper reporting on Schedule D and Form 8949. Inaccurate reporting may trigger IRS notices or audits.
• Economic substance concerns: If transactions appear to lack economic substance (for example, selling and immediately repurchasing nearly identical securities solely for tax purposes), the IRS could potentially challenge the deductions under the economic substance doctrine (IRC Section 7701(o)).
• Related party transactions: Losses on sales to related parties (as defined in IRC Section 267) are generally disallowed. This includes sales to a spouse, siblings, ancestors, lineal descendants, and certain entities.

Maintaining thorough records of all transactions, including dates, amounts, cost bases, and the rationale for replacement security selections, is generally considered a best practice for supporting tax loss harvesting claims in the event of an audit.

Tax Loss Harvesting for 2024 and 2025

For the 2024 tax year, the capital gains rate thresholds, the $3,000 ordinary income offset limit, and the wash sale rules remain consistent with prior years. For 2025, the IRS has announced updated income thresholds under Revenue Procedure 2024-40, with the 0% long-term capital gains rate applying to taxable income up to $48,350 for single filers and $96,700 for married couples filing jointly.

One consideration for 2025 and beyond is the potential for legislative changes. Several provisions of the Tax Cuts and Jobs Act (TCJA) of 2017 are scheduled to sunset after 2025, which could affect ordinary income tax rates and, consequently, the relative benefit of offsetting ordinary income with capital losses. Taxpayers may want to consider the current and projected tax environment when planning loss harvesting strategies.

Timing Considerations

While tax loss harvesting is often associated with year-end planning, opportunities may arise throughout the year. Market downturns during any month can create unrealized losses worth harvesting. Some investors and advisors practice “year-round” tax loss harvesting, monitoring portfolios continuously for opportunities. However, more frequent harvesting also increases the complexity of wash sale tracking and record-keeping.

For year-end harvesting in 2024, it is important to note that the trade date (not the settlement date) generally determines when a gain or loss is realized for tax purposes. Trades must typically be executed by December 31 to count for the current tax year.

Who Benefits Most from Tax Loss Harvesting

Tax loss harvesting typically provides the greatest benefit to:

1. High-income taxpayers in the 32%, 35%, or 37% ordinary income brackets, where the $3,000 deduction against ordinary income produces larger absolute tax savings.
2. Investors with significant realized capital gains from the sale of appreciated securities, real estate (in conjunction with other planning), or business interests.
3. Taxpayers subject to the 3.8% Net Investment Income Tax, who may reduce their NIIT liability by lowering net investment income through harvested losses.
4. Investors with long time horizons, who may benefit from the compounding effects of deferred tax payments over many years.

Conversely, taxpayers in the 0% long-term capital gains bracket may find limited benefit, as their capital gains are already taxed at 0%. Similarly, investors with primarily tax-advantaged accounts (401(k)s, IRAs) generally cannot harvest losses from those accounts.

Data Sources

• IRS Publication 550 (Investment Income and Expenses), 2024 edition, covering capital gains, losses, wash sales, and the $3,000 ordinary income deduction limit.
• IRS Publication 544 (Sales and Other Dispositions of Assets), 2024 edition, covering holding periods and classification of gains and losses.
• Internal Revenue Code Section 1091, governing the wash sale rule for loss disallowance on substantially identical securities.
• Internal Revenue Code Section 1411, governing the 3.8% Net Investment Income Tax and applicable thresholds.
• Internal Revenue Code Section 1014, governing the step-up in basis for inherited property.
• Internal Revenue Code Section 267, governing loss disallowance for related party transactions.
• Internal Revenue Code Section 7701(o), codifying the economic substance doctrine.
• IRS Revenue Procedure 2023-34, establishing inflation-adjusted tax brackets and capital gains thresholds for the 2024 tax year.
• IRS Revenue Procedure 2024-40, establishing inflation-adjusted tax brackets and capital gains thresholds for the 2025 tax year.
• Tax Foundation, “Federal Capital Gains Tax Rates, 1954-2024,” for historical and current capital gains rate data.