Updated October 17, 2026. Quick answer: Code W on Form 8949 goes in column (f) when part of a loss is disallowed under the wash sale rules. The instructions say to “enter the amount of the nondeductible loss as a positive number in column (g).” The code and the adjustment are entered on the same row as the sale.
Schedule D and Schedule E (Form 1040) for 2025, read line by line: Schedule D lines 1b, 2 and 3, Schedule D lines 6 and 7 and Schedule D lines 8b, 9 and 10.
What code W means
The Form 8949 instructions list code W for one situation: “nondeductible loss from a wash sale”. The Schedule D instructions explain what makes a sale a wash sale, and they also say how the row is set up: “Report a wash sale transaction in Part I or Part II (depending on how long you owned the stock or securities) of Form 8949 with the appropriate box checked. Complete all columns. Enter “W” in column (f). Enter as a positive number in column (g) the amount of the loss not allowed.”
In plain terms, you still report the sale, with the proceeds in column (d) and the basis in column (e), and code W tells the IRS that part of the resulting loss is not allowed. Which box to check at the top is covered in the box A to L guide. A loss that is nondeductible for a reason other than a wash sale uses a different code, covered on Form 8949 code L.
The 30-day rule, as Publication 550 words it
Publication 550 states the rule this way: “A wash sale occurs when you sell or trade stock or securities at a loss and within 30 days before or after the sale you” do one of four things. The publication lists them: “Buy substantially identical stock or securities,” “Acquire substantially identical stock or securities in a fully taxable trade,” “Acquire a contract or option to buy substantially identical stock or securities,” or “Acquire substantially identical stock for your individual retirement arrangement (IRA) or Roth IRA.”
The window runs on both sides of the sale. Publication 550 adds that “If you sell stock and your spouse or a corporation you control buys substantially identical stock, you also have a wash sale.” The plain-language walkthrough of the rule, with the timeline, is on the wash sale rule page.
What to enter in column (g)
The code W row in the instructions says “Report the sale or exchange on Form 8949 and enter the amount of the nondeductible loss as a positive number in column (g).” The positive sign matters because column (g) is added to the gain or loss: a positive adjustment shrinks a loss.
As an illustration, not an IRS example: suppose you sold shares for $750 that had a basis of $1,000, and the whole $250 loss is a wash sale loss. Column (d) is $750, column (e) is $1,000, and column (g) is $250. Column (h) is $750 minus $1,000 plus $250, which is $0, so no loss is deducted on that row. The same arithmetic with a partly disallowed loss would leave the allowed part of the loss in column (h).
When the broker’s number is missing or wrong
Your Form 1099-B or Form 1099-DA may show the disallowed loss. The Schedule D instructions explain that “box 1g of Form 1099-B or box 1i of Form 1099-DA will generally show whether there was any nondeductible wash sale loss and its amount” in certain cases. They also warn: “However, you can’t deduct a loss from a wash sale even if it isn’t reported on Form 1099-B or Form 1099-DA (or substitute statement).” The box is explained on the Form 1099-B box 1g page and, for digital assets, on the Form 1099-DA box 1h and 1i page.
If the broker’s amount is off, the code W row says “If you received a Form 1099-B or Form 1099-DA (or substitute statement) and the amount of nondeductible wash sale loss shown in box 1g on Form 1099-B or box 1i on Form 1099-DA is incorrect, enter the correct amount of the nondeductible loss as a positive number in column (g).” If your figure is smaller, “attach a statement explaining the difference.” And where the broker reported something but none of it is a wash sale loss, “If no part of the loss is a nondeductible loss from a wash sale transaction, enter -0- in column (g).”
What happens to the disallowed loss
Publication 550 says the loss is not simply gone: “If your loss was disallowed because of the wash sale rules, add the disallowed loss to the cost of the new stock or securities (except in (4) above). The result is your basis in the new stock or securities.” It also says “This adjustment postpones the loss deduction until the disposition of the new stock or securities.” On timing, “Your holding period for the new stock or securities includes the holding period of the stock or securities sold.” Those basis and holding period effects show up on the later sale, not on this row.
Setting up the row
Columns (f) and (g) work as a pair. “In order to explain any adjustment to gain (or loss) in column (g), enter the appropriate code(s) in column (f).” The dollar side is described this way: “Enter in this column any necessary adjustments to gain (or loss). Enter negative amounts in parentheses.” Most rows need neither: “For most transactions, you don’t need to complete columns (f) and (g) and can leave them blank.”
If a row needs more than one code, the instructions say “Don’t separate the codes by a space or comma.” They also give the rule for the dollar amount: “If you entered more than one code in column (f) on the same row, enter the net adjustment in column (g).”
Where it goes next
Column (h) is where the adjustment lands. The instructions say “First, subtract the cost or other basis in column (e) from the proceeds (sales price) in column (d). Then take into account any adjustments in column (g). Enter the gain (or loss) in column (h).”
The row then flows to the summary. “The total of the amounts in column (h) of line 2 of all your Forms 8949 should equal the amount you get by combining columns (d), (e), and (g) on the corresponding line of Schedule D (Form 1040).” The Schedule D page explains the lines that total comes from, and the Form 8949 instructions page covers the form as a whole.
Edition and line numbers
This page reads the 2025 Form 8949 and its 2025 instructions, along with the 2025 Instructions for Schedule D (Form 1040) (and Publication 550 for 2025 returns where it is cited), the current files irs.gov served on 2026-10-17. They are the forms for the tax year 2025 return, filed in 2026. Check the tax year printed on the form you are filling in and use the column letters and codes on that year’s form, because a different year’s form can letter its columns or word its codes differently.
Common mistakes
- Entering the wash sale loss as a negative number. The instructions say to enter it “as a positive number in column (g).” It is an add-back that offsets part of the loss.
- Trusting the broker form alone. The Schedule D instructions say “you can’t deduct a loss from a wash sale even if it isn’t reported on Form 1099-B or Form 1099-DA (or substitute statement).” A purchase in another account can still trigger the rule.
- Skipping the explanation when your number is smaller than the broker’s. The instructions say “attach a statement explaining the difference.”
Related: Wash sale rule, Form 1099-B box 1g, Form 1099-DA box 1h and 1i, Form 8949 instructions, and Schedule D.
Sources
- Instructions for Form 8949 (2025): https://www.irs.gov/pub/irs-pdf/i8949.pdf
- Instructions for Schedule D (Form 1040) (2025): https://www.irs.gov/pub/irs-pdf/i1040sd.pdf
- Publication 550, Investment Income and Expenses (for 2025 returns): https://www.irs.gov/pub/irs-pdf/p550.pdf
Read from the IRS documents linked above on October 17, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.