Wash sale rule

Expanded explanation

The wash sale rule is a United States tax provision that disallows a loss deduction when an investor sells a security at a loss and acquires a substantially identical security within 30 days before or after that sale.

The purpose is to prevent taxpayers from claiming a tax loss while remaining economically invested in the same position. Selling and immediately repurchasing would create a deduction without any real change in exposure, so the rule defers the benefit rather than granting it.

Importantly, a disallowed loss is not destroyed. It is added to the cost basis of the replacement shares and the holding period carries over, so the deduction is recovered when the replacement position is eventually sold.

How it works

The window is 61 days in total: the 30 days before the sale, the day of the sale, and the 30 days after. Any acquisition of a substantially identical security in that window — including a purchase, an option to acquire, or a reinvested dividend — can trigger the rule.

When triggered:

1. The loss is disallowed for the current tax year.
2. The disallowed amount is added to the basis of the replacement shares.
3. The replacement shares inherit the original holding period, which can convert a short-term position into a long-term one.

If only part of the position is replaced, the disallowance is proportional to the number of replacement shares acquired.

Key distinction

Wash sale vs. capital loss limitation. A wash sale defers a specific loss because the position was re-established. The annual limit on deducting net capital losses against ordinary income is a separate rule that applies after wash sales are accounted for, with unused amounts carried forward.

Substantially identical vs. similar. The rule applies to substantially identical securities, not to merely similar ones. Shares of the same company, and generally options or contracts to acquire them, are substantially identical. Two different funds tracking different indices are generally not, though the analysis is fact-specific and two funds tracking the *same* index invites scrutiny. The Internal Revenue Service has not published a bright-line test, so conservatism is warranted.

Why it matters

Tax-loss harvesting — realising losses deliberately to offset gains — is one of the few reliably valuable tax techniques available to ordinary investors. The wash sale rule is the main constraint on doing it, and violations are easy to trigger accidentally.

Three common traps:

• Automatic dividend reinvestment. A reinvestment inside the 61-day window is a purchase and can disallow part of the loss.
• Scheduled contributions. An investor harvesting a loss in a taxable account while a monthly contribution buys the same fund in the same window creates a wash sale without any deliberate action.
• Purchases in another account. The rule applies across accounts held by the taxpayer, including a spouse's account and, in the case of an IRA purchase, with a harsher outcome.

Common misconceptions

• "I lose the deduction permanently." In ordinary taxable-account cases the loss is deferred into the replacement shares' basis, not forfeited.
• "Only the 30 days after the sale count." The window is symmetric; purchases in the 30 days before the sale also count.
• "It only applies within one brokerage account." Brokers report per account, but the rule applies to the taxpayer. Cross-account and spousal purchases are the reader's responsibility to track.
• "Buying in my IRA is a safe workaround." It is the opposite. When the replacement shares are bought in an individual retirement account, the disallowed loss is not added to any taxable basis, so the deduction is effectively lost.
• "It applies to gains." Only losses are affected. A sale at a gain is taxable regardless of repurchase.

Practical handling

Investors harvesting losses commonly pause dividend reinvestment and automatic purchases in the affected security for the window, or move to a genuinely different investment for at least 31 days before returning. Brokers report wash sales on Form 1099-B for covered securities within the same account, but that report will not capture activity in other accounts, which is where most errors originate.

Practitioners treat "substantially identical" as the unsettled edge of the rule. Swapping between two broad index funds run by different providers and tracking different indices is a common harvesting technique; swapping between two funds tracking the identical index is materially more aggressive, and no safe harbour exists.

Other refinements matter at scale: the rule reaches options and short sales, applies to a spouse's purchases, and interacts with the constructive sale and straddle rules for hedged positions. Broker 1099-B reporting adjusts basis only within the same account and for covered securities, so taxpayers with multiple brokers must reconcile manually.

Because a disallowed loss usually shifts into basis rather than disappearing, the cost of an ordinary wash sale is timing rather than absolute — but timing has real value when it moves a deduction across a year in which tax rates or realised gains differ. This is general educational information, not tax advice; individual circumstances should be reviewed with a qualified tax professional.