Form 8949 Capital Gains Adjustment Checklist
A broker gain summary is not the same thing as a reviewed tax model. Form 8949 is the reconciliation layer between Forms 1099-B, 1099-DA, 1099-S, substitute statements, taxpayer basis records, adjustment codes, and Schedule D. This checklist turns that layer into a practical review flow before short-term gains, long-term gains, wash sale adjustments, selling expenses, market discount, and basis corrections enter an after-tax portfolio model.
Last reviewed: June 16, 2026
Four checks before trusting Form 8949 data
Reconciliation layer
The IRS says Form 8949 reconciles amounts reported to the taxpayer and IRS with the amounts reported on the return, and its subtotals carry to Schedule D.
Proceeds first
Instructions say that when a taxpayer receives Form 1099-B, 1099-DA, 1099-S, or a substitute statement, the proceeds shown on that statement are entered in column (d).
Basis status matters
Instructions distinguish transactions with basis reported to the IRS from transactions without basis shown or with basis not reported to the IRS.
Adjustments are explicit
Column (f) and column (g) handle correction codes and amounts, including incorrect basis, selling expenses, nominee reporting, and wash sale code W.
Form 8949 review workflow
Confirm Form 8949 is the right reconciliation layer
The IRS Form 8949 page says the form reconciles amounts reported on Form 1099-B or Form 1099-S, or a substitute statement, with the amounts reported on the return, and that subtotals then carry to Schedule D.
Open source: IRS about Form 8949Complete Form 8949 before the Schedule D lines it feeds
The 2025 Form 8949 instructions say to file Form 8949 with Schedule D and complete it before Schedule D lines 1b, 2, 3, 8b, 9, or 10. A portfolio model should therefore treat Form 8949 as transaction-level support, not as a later summary.
Open source: IRS instructions for Form 8949Enter statement proceeds before accepting a broker gain summary
The instructions say that if the taxpayer receives Form 1099-B, 1099-DA, 1099-S, or a substitute statement, the proceeds shown on that form or statement are always reported in Form 8949 column (d).
Open source: IRS instructions for Form 8949Use the reported basis first when basis was reported to the IRS
The instructions say that if Form 1099-B or Form 1099-DA shows cost or other basis was reported to the IRS, the basis shown on that form is reported in column (e), and needed corrections or adjustments are made in column (g).
Open source: IRS instructions for Form 8949Do not over-file clean covered-security rows
The instructions say a taxpayer may not need to file Form 8949 when all Forms 1099-B or 1099-DA show basis was reported to the IRS and no correction or adjustment is needed. Those clean summary rows may instead flow directly to Schedule D under the stated exception.
Open source: IRS instructions for Form 8949Separate short-term and long-term boxes
The instructions say short-term gains and losses go in Part I and long-term gains and losses go in Part II. The form itself tells taxpayers to check Form 1099-B, Form 1099-DA, or substitute statements before choosing boxes A, B, C, G, H, or I.
Open source: IRS Form 8949 and instructionsRoute missing-basis and nonreported-basis transactions separately
For short-term transactions, the instructions route statement transactions with basis reported to the IRS to box A or G and transactions without basis shown, or with basis not reported to the IRS, to box B or H. Similar long-term logic uses boxes D/J and E/K.
Open source: IRS instructions for Form 8949Use adjustment codes instead of silently replacing the broker record
The instructions say incorrect basis reported to the IRS uses code B and a column (g) adjustment; selling expenses, option premiums, or digital asset transaction costs not reflected on the statement use code E and a column (g) adjustment.
Open source: IRS instructions for Form 8949Check wash sale code W before modeling a tax-loss sale
The instructions say a nondeductible wash sale loss uses code W and the nondeductible loss amount is entered as a positive number in column (g). If the broker's wash sale amount is wrong, the correct nondeductible amount is entered and a statement may be needed when it is lower than the broker amount.
Open source: IRS instructions for Form 8949Carry the reviewed subtotals into Schedule D
The IRS says Schedule D reports the overall gain or loss from transactions reported on Form 8949 and can also report capital gain distributions, capital loss carryovers, and certain transactions that do not have to be reported on Form 8949.
Open source: IRS instructions for Form 8949
Official sources used
IRS about Form 8949
Explains Form 8949's reconciliation role and how subtotals carry to Schedule D.
IRS instructions for Form 8949
Explains proceeds, basis, short-term and long-term boxes, clean covered-security exceptions, adjustment columns, and Schedule D carryover.
IRS Form 8949
Shows the 2025 form layout, including short-term and long-term parts, checkbox groups, and statement guidance.
IRS about Schedule D
Explains when Schedule D reports capital asset sales, involuntary conversions, capital gain distributions, and nonbusiness bad debts.
IRS Schedule D instructions
Explains short-term versus long-term reporting and how capital gain distributions and basis records connect to Schedule D.
Form 8949 FAQ
Is Form 8949 just the same thing as Form 1099-B?
No. Form 1099-B is a broker information return or statement source. IRS guidance describes Form 8949 as the reconciliation form that compares what was reported to the taxpayer and IRS with what the taxpayer reports on the return.
Can clean covered-security trades skip Form 8949?
Sometimes. IRS instructions say Form 8949 may not be needed when all broker statements show basis was reported to the IRS and no correction or adjustment is needed. The summary information can then be reported directly on Schedule D under that exception.
Where do wash sale adjustments show up?
The Form 8949 instructions say a nondeductible wash sale loss uses code W in column (f), and the nondeductible loss is entered as a positive number in column (g). That is why a tax-loss model should check Form 1099-B box 1g and Form 8949 code W together.
This page is general investor education, not tax advice, filing advice, legal advice, or a recommendation about any tax position. Form 8949 reporting can depend on broker statements, covered-security status, taxpayer basis records, digital asset treatment, wash sale rules, market discount, nominee reporting, nonresident rules, estate basis records, and Schedule D instructions.
Continue to the Form 1099-B cost basis checklist
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