Form 1099-B field reference
Form 1099-B Box 4: Federal income tax withheld
Form 8949 destination
Not a Form 8949 gain/loss adjustment
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.
Before filing
What to check
- Match the amount to the year-end broker statement.
- Do not subtract it from Form 8949 proceeds or add it to basis.
- Include it with the federal withholding claimed on Form 1040.