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W-2 Box 12 Codes A and B: Uncollected Tax on Tips

Updated September 29, 2026. Quick answer: code A is the social security (or railroad retirement) tax on your tips that your employer could not collect, and code B is the Medicare tax on your tips that it could not collect. Each reports tax that was not withheld because your pay did not cover it.

Code A: what the IRS tells the employer

The instructions read: “Show the employee social security or Railroad Retirement Tax Act (RRTA) tax on all of the employee’s tips that you could not collect because the employee did not have enough funds from which to deduct it.” They add: “Do not include this amount in box 4.”

Code B: what the IRS tells the employer

The instructions read: “Show the employee Medicare tax or RRTA Medicare tax on tips that you could not collect because the employee did not have enough funds from which to deduct it.” They add: “Do not include this amount in box 6.” And: “Do not show any uncollected Additional Medicare Tax.”

What they are not

Neither code is extra pay. They record tax on tips that was not withheld from your paycheck and is left out of the Box 4 and Box 6 withholding totals. For the uncollected tax on group-term life insurance for former employees see code C.

Common mistakes

  • Reading A or B as income. They report uncollected tax, not wages.
  • Adding code A to Box 4 or code B to Box 6. The instructions say not to.

Related: code C.

Every code in one place: the Box 12 codes table. If a withdrawal from one of these accounts is your question, see the Form 1099-R Box 7 codes.

Figures verified against the IRS 2026 General Instructions for Forms W-2 and W-3 on September 30, 2026.

Sources

Code meanings are read from the IRS 2026 General Instructions for Forms W-2 and W-3 (Box 12) at irs.gov on September 29, 2026. General information, not tax advice. Your own facts decide the outcome, and a payroll professional, a preparer or the IRS is the right place to confirm anything consequential.