Wash Sale Rule Guide 2026: IRS Section 1091, Tax-Loss Harvesting & Crypto

The wash sale rule prevents investors from claiming a tax loss while maintaining essentially the same investment position. It applies to stocks, bonds, mutual funds, options, and other securities — but currently NOT to cryptocurrency. Understanding the wash sale rule is critical for tax-loss harvesting, year-end tax planning, and managing the tax cost of portfolio rebalancing.

How the Wash Sale Rule Works

The wash sale rule has several key mechanics investors must understand:

The 61-Day Window

The wash sale rule applies if you sell a security at a loss AND you purchased or acquired a substantially identical security within the period starting 30 days BEFORE the sale and ending 30 days AFTER the sale. Example: You sell 100 shares of Apple at a $5,000 loss on December 15. If you bought Apple shares between November 15 and January 14 (30 days on each side), the loss is a wash sale. The rule applies to any purchase method: market purchase, dividend reinvestment, stock option exercise, or purchase in an IRA or 401(k).

What Happens to the Disallowed Loss

The disallowed loss is not gone — it is added to the cost basis of the replacement shares. Example: You sell 100 Apple shares at a $5,000 loss, triggering a wash sale. You bought 100 replacement Apple shares at $150/share ($15,000). The $5,000 disallowed loss is added to your basis: new basis = $15,000 + $5,000 = $20,000. When you sell the replacement shares, your basis is $20,000 — the $5,000 loss is effectively preserved for that future sale.

Substantially Identical Securities

The IRS has not defined 'substantially identical' precisely, but clear guidance exists for common cases:

• Same stock ticker: Clearly substantially identical — selling AAPL and rebuying AAPL within 30 days triggers wash sale.
• Options on the same stock: Selling AAPL stock at a loss and buying AAPL call options is likely a wash sale.
• Mutual funds tracking the exact same index: Selling Vanguard S&P 500 (VFINX) and buying Fidelity 500 Index (FXAIX) — both track the S&P 500. IRS has stated these may be substantially identical. However, selling a fund tracking the S&P 500 and buying a different fund tracking the Nasdaq 100 is NOT substantially identical.
• Different sector ETFs: Selling XLK (tech ETF) and buying QQQ (Nasdaq 100) — generally NOT substantially identical (different holdings, different index). This is a common tax-loss harvesting strategy: sell at a loss and replace with a similar (but not identical) fund.
• Different companies in the same industry: Selling Ford at a loss and buying GM is NOT a wash sale — they are different companies, not substantially identical.

The IRA Wash Sale Trap

This is the most costly wash sale mistake: you sell a stock at a loss in a taxable brokerage account, then buy the same stock in your IRA or Roth IRA within 30 days. This triggers a wash sale. However, unlike a taxable account where the basis is adjusted, the IRA cannot accept a basis adjustment. The $5,000 loss is permanently disallowed — not added to any basis anywhere. The loss is gone forever. Avoid buying in an IRA any security you have sold at a loss in a taxable account in the prior 30 days, or plan to sell at a loss in the next 30 days.

Tax-Loss Harvesting Strategies Around the Wash Sale Rule

Tax-loss harvesting realises investment losses to offset capital gains, while maintaining market exposure:

The Basic Strategy

You own S&P 500 ETF (VOO). It has declined 15%. You sell VOO to harvest the $10,000 loss. You immediately buy a different S&P 500 ETF — say, iShares S&P 500 (IVV). IVV tracks the same S&P 500 but is a different fund from a different provider. Whether VOO and IVV are 'substantially identical' is debated — both track the same index, have nearly identical holdings, and nearly identical performance. The IRS has not specifically ruled on this. Most tax professionals use funds tracking different (but correlated) indexes to be safe: sell S&P 500 ETF (VOO), buy Total Market ETF (VTI) — different index, different holdings, not substantially identical.

30-Day Wait Strategy

If you want to repurchase the exact same security: sell at a loss, wait 31 days, then rebuy. This avoids the wash sale window entirely. Risk: the market moves against you during the 31-day wait (you miss a 10% rally). This strategy accepts market risk in exchange for tax certainty.

Cryptocurrency Tax-Loss Harvesting

As of 2026, cryptocurrency (Bitcoin, Ethereum, altcoins) is NOT subject to the wash sale rule. The IRS classifies crypto as property, not securities — and Section 1091 applies only to stock and securities. This means you can: sell Bitcoin at a $20,000 loss, immediately rebuy Bitcoin, and claim the full $20,000 loss. No 30-day wait required. This makes crypto tax-loss harvesting much more straightforward than stock harvesting. Warning: proposed legislation (included in various tax bills since 2021) would apply wash sale rules to crypto — if enacted, this advantage would end. Monitor legislation if you rely on crypto harvesting.

Year-End Tax-Loss Harvesting

December is peak tax-loss harvesting season. Key rules: (1) Losses must be realized by December 31 to offset 2026 gains; (2) Remember the 30-day look-back — if you bought securities in late November, selling in December creates potential wash sale if you rebought within November; (3) Net long-term losses offset long-term gains first; net short-term losses offset short-term gains first — excess of either type offsets the other; (4) Up to $3,000 of net capital losses can offset ordinary income per year; (5) Unused losses carry forward indefinitely.