Updated October 17, 2026. Quick answer: Form 8949 has one checkbox at the top of each part, and you check only one per part. Boxes A, B, C, G, H and I are in Part I for short-term sales, and boxes D, E, F, J, K and L are in Part II for long-term sales. The letter you pick depends on whether you got a Form 1099-B, a Form 1099-DA or neither, and whether the form shows the basis was reported to the IRS.
Read box by box from the IRS form text: Form 1099-CAP boxes 1 to 5.
Schedule D and Schedule E (Form 1040) for 2025, read line by line: Schedule D line 8a, Schedule D lines 8b, 9 and 10 and Schedule D line 18.
What the boxes do
Every transaction on Form 8949 sits under one checkbox. The form says so at the top of each part. In Part I: “You must check Box A, B, C, G, H, or I below. Check only one box.” In Part II: “You must check Box D, E, F, J, K, or L below. Check only one box.” The instructions explain why you may need several copies: “Use a separate Part I for each type of short-term transaction described in the text for one of the boxes (A, B, C, G, H, or I) at the top of Part I.” The same instruction for Part II reads “Use a separate Part II for each type of long-term transaction described in the text for one of the boxes (D, E, F, J, K, or L) at the top of Part II.”
The full set of instructions is on Form 8949 instructions, and the totals end up on Schedule D.
Part I or Part II: short term or long term
The part is set by how long you held the property. The form’s Part I heading says “Transactions involving capital assets you held 1 year or less are generally short-term”. Part II says “Transactions involving capital assets you held more than 1 year are generally long-term”. So the first choice is the part, and the second is the letter within that part.
The twelve boxes side by side
Each part has six boxes, and the pattern repeats. Letters A to C and D to F go with Form 1099-B and with sales that have no form. Letters G to I and J to L are the Form 1099-DA set. The form’s own wording is in the last column.
| Box | Part | Form that reported it | Form 8949 wording |
|---|---|---|---|
| A | Part I, short term | Form 1099-B | “Short-term transactions reported on Form(s) 1099-B showing basis was reported to the IRS” |
| B | Part I, short term | Form 1099-B | “Short-term transactions reported on Form(s) 1099-B showing basis was not reported to the IRS” |
| C | Part I, short term | None | “Short-term transactions, other than digital asset transactions, not reported to you on Form 1099-B or Form 1099-DA” |
| G | Part I, short term | Form 1099-DA | “Short-term transactions reported on Form(s) 1099-DA showing basis was reported to the IRS” |
| H | Part I, short term | Form 1099-DA | “Short-term transactions reported on Form(s) 1099-DA showing basis was not reported to the IRS” |
| I | Part I, short term | None | “Short-term digital asset transactions not reported to you on Form 1099-DA or Form 1099-B” |
| D | Part II, long term | Form 1099-B | “Long-term transactions reported on Form(s) 1099-B showing basis was reported to the IRS” |
| E | Part II, long term | Form 1099-B | “Long-term transactions reported on Form(s) 1099-B showing basis was not reported to the IRS” |
| F | Part II, long term | None | “Long-term transactions, other than digital asset transactions, not reported to you on Form 1099-B or Form 1099-DA” |
| J | Part II, long term | Form 1099-DA | “Long-term transactions reported on Form(s) 1099-DA showing basis was reported to the IRS” |
| K | Part II, long term | Form 1099-DA | “Long-term transactions reported on Form(s) 1099-DA showing basis was not reported to the IRS” |
| L | Part II, long term | None | “Long-term digital asset transactions not reported to you on Form 1099-DA or Form 1099-B” |
Boxes A, D, G and J: basis was reported to the IRS
Part I with box A or box G is described this way: “Report on Part I with box A or box G checked all short-term transactions reported to you on Form 1099-B or Form 1099-DA (or substitute statement) with an amount shown for cost or other basis unless the statement indicates that amount wasn’t reported to the IRS.” For Part II, “Report on Part II with box D or box J checked all long-term transactions reported to you on Form 1099-B or Form 1099-DA (or substitute statement) with an amount shown for cost or other basis unless the statement indicates that amount wasn’t reported to the IRS.”
Form 1099-B and Form 1099-DA each show whether the basis went to the IRS. See the pages on Form 1099-B boxes 5 and 12 and Form 1099-DA boxes 2 and 9 for where that is shown. The instructions also point to a shortcut on the statement itself: “the “Applicable checkbox on Form 8949″ box near the top of that form may help you determine which box to check”.
Boxes B, E, H and K: no basis, or basis not reported
The second letter in each group is for a statement with no usable basis. “Report on Part I with box B or box H checked all short-term transactions reported to you on Form 1099-B or Form 1099-DA (or substitute statement) without an amount shown for cost or other basis or showing that cost or other basis wasn’t reported to the IRS.” The long-term version is “Report on Part II with box E or box K checked all long-term transactions reported to you on Form 1099-B or Form 1099-DA (or substitute statement) without an amount shown for cost or other basis or showing that cost or other basis wasn’t reported to the IRS.”
The instructions give a way to tell which side of the line you are on: “If your statement shows cost or other basis but indicates it wasn’t reported to the IRS (for example, if box 12 on Form 1099-B or box 2 on Form 1099-DA isn’t checked), see Box B or Box H below.” If basis is wrong on a box B or box E row, the fix is in the column (e) entry, as explained on Form 8949 code B.
Boxes C, F, I and L: no Form 1099-B or Form 1099-DA
The third letter in each group is for sales you did not get a form for. Box C or box I is for the short-term sales left over, those for which you can’t check box A, B, G or H because you didn’t receive a Form 1099-B or Form 1099-DA (or substitute statement). Then comes the digital asset rule: “Do not use box C to report digital asset transactions. Use box I.” For long-term sales, “Do not use box F to report digital asset transactions. Use box L.”
One box covers everything, or you use several pages
You do not always fill in both parts. The instructions say “You don’t need to complete and file an entire copy of Form 8949 (Parts I and II) if you can check a single box to describe all your transactions.” “In that case, complete and file either Part I or II and check the box that describes the transactions.” “Otherwise, complete a separate Part I or II for each category of your transactions, as described above.”
Where it goes next
Once every row is complete, the instructions say “Include on your Schedule D the totals from all your Parts I and II.” “Form 8949 and Schedule D explain how to do this.” For the Schedule D side, see Schedule D and the Form 1040 page. If the row also carries a column (f) code, such as Form 8949 code E or Form 8949 code W, the code goes on the same row under whichever box applies.
Edition and line numbers
This page reads the 2025 Form 8949 and its 2025 instructions, along with the Publication 550 edition for 2025 returns where cited, the current files irs.gov served on 2026-10-17, 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
- Checking more than one box on a page. Each part says “Check only one box.” A second type of sale needs its own copy of the part.
- Using box C or box F for a digital asset sale. The instructions say “Do not use box C to report digital asset transactions. Use box I.” The long-term version points to box L.
- Treating every Form 1099-B or Form 1099-DA row as basis reported. The instructions say “If your statement shows cost or other basis but indicates it wasn’t reported to the IRS”, the sale goes under the second letter in the group (B, E, H or K) instead.
Related: Form 8949 instructions, Schedule D (Form 1040), Form 1099-B boxes 5 and 12, Form 1099-DA boxes 2 and 9, and Form 1040.
Sources
- Instructions for Form 8949 (2025): https://www.irs.gov/pub/irs-pdf/i8949.pdf
- Form 8949 (2025): https://www.irs.gov/pub/irs-pdf/f8949.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.