Wash Sale
Key Takeaways
- A wash sale occurs when you sell a security at a loss and buy a substantially identical one within 30 days
- The wash sale rule disallows the capital loss deduction when triggered
- The disallowed loss is added to the cost basis of the replacement shares
- The rule applies across all accounts, including IRAs and spouse's accounts
Definition
A wash sale occurs when an investor sells a security at a loss and purchases a "substantially identical" security within 30 days before or after the sale. The wash sale rule, established under IRS Section 1091, disallows the capital loss deduction on the original sale to prevent taxpayers from claiming artificial losses while maintaining their investment position.
The wash sale window spans 61 days: 30 days before the sale, the day of the sale, and 30 days after the sale. Any purchase of a substantially identical security within this window triggers the rule. The disallowed loss is not permanently lost — it is added to the cost basis of the replacement shares, deferring the tax benefit to a future sale.
The wash sale rule applies across all accounts an investor owns, including taxable accounts, IRAs, and even a spouse's accounts in some interpretations. This broad application makes it important to coordinate transactions across all accounts when harvesting losses.
How It Works
When a wash sale is triggered, the disallowed loss is added to the cost basis of the replacement shares, and the holding period of the original shares carries over. For example, if you sold 100 shares at a $1,000 loss and repurchased 100 shares within 30 days, the $1,000 loss is disallowed and your cost basis on the new shares increases by $1,000. When you eventually sell the replacement shares, you will recognize the previously disallowed loss through the higher cost basis.
The IRS has not explicitly defined "substantially identical," but it clearly includes the same stock or security. For mutual funds and ETFs, the guidance is less clear, but selling one S&P 500 index fund and buying a nearly identical one from a different provider could potentially trigger the rule. Different indices (e.g., selling an S&P 500 fund and buying a total market fund) are generally considered sufficiently different.
Investors practicing tax-loss harvesting must be especially careful about wash sales. Automatic dividend reinvestment, automatic investment plans, and purchases in different accounts can inadvertently trigger wash sales and disallow valuable loss deductions.
Example
On December 10, you sell 200 shares of a technology ETF for a $3,000 loss to harvest the tax benefit. On December 28 (18 days later), you purchase 200 shares of the same ETF at a slightly lower price. Because you repurchased a substantially identical security within 30 days, this is a wash sale. The $3,000 loss is disallowed on your current tax return. However, the $3,000 is added to your cost basis on the new shares. If you later sell the replacement shares for a $5,000 gain, your taxable gain would be only $2,000 ($5,000 gain minus the $3,000 disallowed loss now embedded in cost basis).
Why It Matters
The wash sale rule is a critical consideration for any investor engaged in tax-loss harvesting or selling investments at a loss. Violating the rule does not result in penalties, but it defers the tax benefit you were trying to capture, defeating the purpose of the loss sale. Proper understanding of the rule allows investors to harvest losses legally and efficiently.
As year-end tax planning becomes common, awareness of the wash sale window is essential. Many inadvertent wash sales occur in December when investors sell losing positions without considering automatic reinvestments or purchases scheduled in January. Coordinating all transactions across all accounts is key to avoiding this pitfall.
Advantages
- Disallowed losses are not permanently lost — they increase the replacement shares' cost basis
- The holding period of the original shares carries over to the replacement shares
- Understanding the rule enables effective tax-loss harvesting strategies
- Many brokers now flag potential wash sales on tax reporting documents
Limitations
- Defers rather than eliminates the tax benefit of the loss
- Applies across all accounts, making coordination complex
- The definition of 'substantially identical' is vague for funds and ETFs
- Automatic reinvestment programs can trigger unintended wash sales
Frequently Asked Questions
Related Terms
Browse more definitions in the financial terms glossary.