Wash sale calculator
List the trades of ONE security in order. Losing sales get matched against purchases within 30 days before or after; the tool splits your losses into what counts this year and what the wash sale rule defers into the replacement shares.
The verdict
Loss allowed this year$0
- Total realized losses
- $300
- Washed (deferred into basis)
- $300
Wash events
- Sale on 2026-03-01 washed by the 2026-03-11 purchase: $300 deferred
Estimate
workingfigures.com/calculators/wash-sale-calculator
How the matching works
Basis per sale is FIFO. A sale at a loss is washed by purchases of the same security within ±30 days (nearest first), proportionally to the replacement shares still held; the disallowed loss is added to the replacement basis, not destroyed.
Assumptions
One security per run, one account. The rule also crosses accounts (including IRAs, where the loss dies) and reaches substantially identical securities and options; those judgment calls are yours to add. Directly-held crypto is not covered by the rule as of our last check. General information, not tax advice.
FAQ
- The loss is disallowed. Is it gone?
- No: it moves into the cost basis of the replacement shares, so it returns when you finally sell them outside the window. In a taxable account a wash is deferral, not destruction. The exception is repurchasing inside an IRA, where the loss is permanently lost.
- Do dividend reinvestments trigger washes?
- Yes, and it is the classic accident: a tiny automatic reinvestment within the window washes a proportional slice of a large harvested loss. Pause automatic reinvestment in a security you plan to harvest, or harvest in a fund the plan does not touch.
- My broker already reports wash sales. Why check?
- Brokers flag washes within one account. Purchases in your other accounts, your spouse\u2019s, or your IRA are invisible to them and still count. This tool models one list of trades; combining the accounts into that list is exactly the work worth doing before year-end.