Updated October 18, 2026. Quick answer: Line 1a is an optional shortcut for short-term sales on a Form 1099-B or 1099-DA where the broker reported your basis to the IRS and you have no adjustments. You add up proceeds and cost from those forms, enter the totals, and figure the gain or loss in column (h). Anything that needs an adjustment goes on Form 8949 instead.
What line 1a asks for
The form captions line 1a as “Totals for all short-term transactions reported on Form 1099-B or Form 1099-DA for which basis was reported to the IRS and for which you have no adjustments”. The caption adds an escape hatch: “However, if you choose to report all these transactions on Form 8949, leave this line blank and go to line 1b”. So line 1a is a choice, not a requirement. It sits in Part I of Schedule D (Form 1040). Part I covers short-term sales, and the instructions say “Report short-term gains or losses in Part I.” On holding periods they say “The holding period for short-term capital gains and losses is generally 1 year or less.”
Which sales can go on line 1a
The instructions say you can use this line for “the aggregate totals from any transactions (except sales of collectibles) for which:” Each of these must be true:
- “You received a Form 1099-B or Form 1099-DA (or substitute statement) that shows basis was reported to the IRS and doesn’t show any adjustments in box 1f or 1g (Form 1099-B) or box 1h or 1i (Form 1099-DA);”
- “The Ordinary box in box 2 on Form 1099-B isn’t checked;”
- “The QOF box in box 3 on Form 1099-B isn’t checked;”
- “You don’t need to make any adjustments to the basis or type of gain or loss reported on Form 1099-B or Form 1099-DA (or substitute statement), or to your gain or loss.”
The full list in the instructions also covers the matching Form 1099-DA boxes and requires that you are not electing to defer income due to an investment in a qualified opportunity fund and are not terminating deferral from such an investment, so read it against your own statement. The boxes on a Form 1099-B are explained on the 1099-B box 5 and box 12 page, and the proceeds and basis boxes are on the 1099-B box 1d and 1e page.
Where the number comes from
The instructions give the arithmetic: “Figure gain or loss on each line. Subtract the cost or other basis in column (e) from the proceeds (sales price) in column (d). Enter the gain or loss in column (h). Enter negative amounts in parentheses.” Your proceeds and basis come straight from the Form 1099-B or 1099-DA you received. The instructions also lighten the paperwork: “If you choose to report these transactions on lines 1a and 8a, don’t report them on Form 8949.” “You don’t need to attach a statement to explain the entries on lines 1a and 8a”. The instructions’ first worked example uses line 8a, which has the same layout; it is walked through on the Schedule D line 8a page.
When a sale does not belong on line 1a
The instructions give two cases. In the first, basis was not reported: “Box 12 on Form 1099-B or box 2 on Form 1099-DA isn’t checked, meaning that basis wasn’t reported to the IRS.” “Don’t report this transaction on line 1a or line 8a. Instead, report the transaction on Form 8949.” In the second, the reported basis is wrong: “However, the basis shown (in box 1e on Form 1099-B or box 1g on Form 1099-DA) is incorrect.” That sale also goes on Form 8949. Details on the boxes and codes are on the Form 8949 page and the Form 8949 boxes A to L guide. Once you have decided what goes on Form 8949, finish it first: “Complete all necessary pages of Form 8949 before completing line 1b, 2, 3, 8b, 9, or 10 of Schedule D.” Those lines are covered at Schedule D lines 1b, 2 and 3.
Where it goes next
Line 1a feeds the Part I total. Line 7 is captioned “Net short-term capital gain or (loss). Combine lines 1a through 6 in column (h).” That combining step is explained at Schedule D lines 6 and 7. Line 7 then flows into the Part III summary, covered at Schedule D lines 16 and 17.
Edition and line numbers
This page reads the 2025 Schedule D (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are byte-identical to the archived copies and they are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040, 1040-SR, or 1040-NR.” Schedule D has its own instructions booklet, titled “Instructions for Schedule D (Form 1040)”. Check the tax year printed on the schedule you are filling in and use the line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Putting a sale on line 1a when basis was not reported to the IRS. The instructions say “Don’t report this transaction on line 1a or line 8a. Instead, report the transaction on Form 8949.”
- Using line 1a when the basis on the statement is wrong or needs an adjustment. The test is that “You don’t need to make any adjustments to the basis or type of gain or loss reported on Form 1099-B or Form 1099-DA (or substitute statement), or to your gain or loss.”
- Reporting the same sale twice. The instructions say “If you choose to report these transactions on lines 1a and 8a, don’t report them on Form 8949.”
Related: Schedule D (Form 1040), 1099-B box 5 and box 12, 1099-B box 1d and 1e, Form 8949, and Form 8949 boxes A to L.
Sources
- Instructions for Schedule D (Form 1040), Capital Gains and Losses (2025): https://www.irs.gov/pub/irs-pdf/i1040sd.pdf
- Schedule D (Form 1040), Capital Gains and Losses (2025): https://www.irs.gov/pub/irs-pdf/f1040sd.pdf
Read from the IRS documents linked above on October 18, 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.