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Form 1099-B field reference

Form 1099-B Box 12: Basis reported to the IRS

Form 8949 destination

Helps select box A/D versus B/E

Reconcile this field with the rest of the transaction before calculating gain or loss. A Form 1099-B label does not override the official basis, holding-period, or adjustment rules.

Box 12

Basis reported to the IRS

Open Form 8949 worksheet →

Before filing

What to check

  • Read the broker statement's basis-reporting indicator.
  • Do not confuse basis reported to you with basis reported to the IRS.
  • Use Form 8949 adjustments when the reported basis must be corrected.

Continue the capital-gains filing flow

Form 1099-B guide Form 8949 worksheet Schedule D guide Capital gains calculator

Sources