Updated September 29, 2026. Quick answer: code AA in Box 12 is your designated Roth contributions to a 401(k) plan for the year. Unlike code D pre-tax deferrals, Roth contributions are still taxable wages, so they are reported in Boxes 1, 3 and 5 as well.
What the IRS tells the employer
The instructions read: “Use this code to report designated Roth contributions under a section 401(k) plan. Do not use this code to report elective deferrals under code D.”
Why Roth is reported twice
On the tax treatment the instructions say: “Designated Roth contributions are subject to federal income tax withholding and social security and Medicare taxes (and railroad retirement taxes, if applicable) and must be reported in boxes 1, 3, and 5.” Separately, “Section 402A requires separate reporting of the yearly designated Roth contributions.” Box 12 is where that separate reporting happens.
What a designated Roth contribution is
The instructions define the term: “Under section 402A, a participant in a section 401(k) plan, under a 403(b) salary reduction agreement, or in a governmental 457(b) plan that includes a qualified Roth contribution program, may elect to make designated Roth contributions to the plan or program in lieu of elective deferrals.”
An example from the IRS
In the instructions’ 401(k) example, “The designated Roth contribution is reported in box 12 with code AA (AA 1000.00).” The same example reports the pre-tax deferral separately under code D.
Common mistakes
- Looking for AA amounts to be missing from Box 1. Roth contributions are included there, unlike pre-tax code D deferrals.
- Adding D and AA into one number. The instructions call for separate Box 12 entries for each.
Related: code D, code BB, code EE, Roth 401(k) required minimum distributions, and what Roth versus pre-tax does to a paycheck.
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
- IRS, 2026 General Instructions for Forms W-2 and W-3: https://www.irs.gov/pub/irs-pdf/iw2w3.pdf
- IRS, About Form W-2, Wage and Tax Statement: https://www.irs.gov/forms-pubs/about-form-w-2
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How our partner relationships workCode 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.