What Does Box 12 Code AA Mean on a W-2?

Roth 401(k) contribution (after-tax) — what it means, whether it's taxable, and what to do with it.

By the Easy Guides Editorial Team · Updated for 2026

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Quick answer

Code AA in Box 12 of your W-2 means roth 401(k) contribution (after-tax). Tax treatment: After-tax.

What Code AA means

The payoff comes later: qualified Roth 401(k) withdrawals in retirement are tax-free. Code AA just documents how much you put in.

Does Code AA affect my taxes?

Your Roth 401(k) contribution. Because it's made after tax, it's already in your Box 1 wages and there's no deduction now.

Where to find Code AA on your W-2

Box 12 has up to four slots — labeled 12a, 12b, 12c, and 12d. Each slot shows a letter code and a dollar amount. The 12a–12d labels are just line numbers; the actual code is the small letter next to the money. So "12a: AA 5,000" means Code AA with a $5,000 amount. When you file, enter the code and amount exactly as shown.

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Frequently asked questions

Your Roth 401(k) contribution. Because it's made after tax, it's already in your Box 1 wages and there's no deduction now.
Enter the code and amount into your tax software exactly as they appear on the W-2. The software handles the rest — you don't calculate anything by hand.
Box 12 has up to four slots labeled 12a, 12b, 12c, and 12d. Each slot holds a letter code and a dollar amount. The small letter (like AA) is the code; the number next to it is the amount. The 12a–12d labels are just line labels, not codes.

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