What does the wash-sale rule review?
IRS Publication 550 says a loss from a stock or securities sale generally cannot be deducted if, during the 30 days before or after the sale, the taxpayer acquires substantially identical stock or securities in specified ways. The rule also covers certain contracts and options. A date match alone is not enough: whether two investments are substantially identical depends on the facts, so this worksheet never makes that decision.
How should I use this worksheet?
Enter each relevant purchase lot and each sale that realized a loss. Use the same comparison label to ask the worksheet to screen those rows together; the label can be a ticker or a note you choose, but it is only a search key. Dates are compared as calendar dates, including the 30th day before and after the sale. Confirm the full transaction history across accounts and review potentially related securities, options, and other circumstances separately.
For each candidate purchase, manually enter the shares you determine should be matched after reviewing the facts. The displayed loss amount is the loss per sold share multiplied by those manually matched shares, limited to the sale and purchase quantities. The illustrative replacement basis per share adds that per-share loss to the purchase lot’s original cost per share. If a purchase lot appears against more than one sale, allocate shares across those rows yourself and check that the total does not exceed the lot. The calculation is a worksheet scenario, not a tax conclusion.
What is the IRS basis adjustment example?
Publication 550’s example sells 100 shares for a $1,000 loss after buying 50 replacement shares for $2,750 and 25 for $1,125 within the window. It explains that $750 of loss is disallowed on 75 shares. The $500 portion is added to the first lot, making its basis $3,250; the remaining $250 is added to the second lot, making its basis $1,375. The remaining 25 shares of the sale retain a deductible $250 loss in that example. The IRS says the disallowed loss is generally added to replacement-share cost, postponing the deduction until those shares are disposed of, subject to exceptions and details in the publication.
What should I verify before filing?
Compare the worksheet with trade confirmations, brokerage tax forms, and the IRS publication for the applicable tax year. Broker reporting may not include every transaction that matters, and an unreported wash sale is not automatically deductible. Publication 550 describes Form 8949 reporting, including code W and the disallowed amount. Ask a qualified tax professional about security identity, account scope, share matching, and special cases.
Source and date: IRS Publication 550 (2025), Investment Income and Expenses, “Wash Sales” (accessed 2026-11-03). Confirm current-year instructions before filing.
Frequently asked questions
Does a matching label mean the securities are substantially identical?
No. The label only groups your rows for a date screen. You must assess security identity using the facts and IRS guidance.
Does the tool find purchases in every account?
No. It can only compare transactions you enter here. Review all relevant accounts and records separately.
Does a candidate row mean my loss is disallowed?
No. It identifies a purchase inside the date window with a matching user-entered label. The rule and share allocation need your review.
Is the adjusted basis a tax filing result?
No. It is arithmetic based on the shares and transactions you manually enter. Verify the proper adjustment and reporting with IRS instructions or a tax professional.