401(k) Contributions on Your W-2: Box 12 Codes, 2026 Limits, and Box 13

On your W-2, 401(k) contributions show up in Box 12. Traditional (pre-tax) deferrals are reported under Code D; Roth 401(k) deferrals are reported under Code AA. The dollar figure next to each code is your total elective deferral for the year, including any catch-up contributions. Those same deferrals also change your wage figures in Boxes 1, 3, and 5, and the change depends on whether you chose traditional or Roth.

How Traditional and Roth Deferrals Change Boxes 1, 3, and 5

Your W-2 reports three separate wage figures, each feeding a different tax. Box 1 is federal taxable wages. Box 3 is Social Security wages. Box 5 is Medicare wages. A traditional 401(k) deferral lowers only one of them. A Roth deferral lowers none.

When you contribute to a traditional 401(k), the amount is subtracted from Box 1 before your employer reports your wages. Earn $80,000 and defer $10,000, and Box 1 shows $70,000. You don’t pay federal income tax on those dollars until you withdraw them in retirement.¹

Boxes 3 and 5 still include the full $80,000. Pre-tax 401(k) deferrals don’t reduce your Social Security or Medicare wages.¹ You still owe the 6.2% Social Security tax (up to the 2026 wage base of $184,500) and the 1.45% Medicare tax on those contributions.² That’s why Box 1 is almost always lower than Boxes 3 and 5 for anyone making pre-tax retirement deferrals.

Roth 401(k) contributions work differently on the front end. Because you’re saving with after-tax dollars, the deferral stays in Box 1. Boxes 3 and 5 also include the Roth amount, just as they would for any other wages.³ The payoff comes later: qualified withdrawals from a Roth 401(k) are tax-free.

So the pattern is simple. Traditional deferrals create a gap between Box 1 and Boxes 3 and 5. Roth deferrals don’t. If you split your contributions between the two during the year, Box 1 will fall somewhere in between.

Reading Box 12 Codes D and AA

Box 12 is where your employer itemizes specific types of compensation and benefits using letter codes.⁴ For 401(k) participants, two codes matter:

Code D: your traditional (pre-tax) elective deferrals to a 401(k) plan.
Code AA: your designated Roth contributions to a 401(k) plan.⁴

If you contributed to both buckets during the year, you’ll see both codes on the same W-2 with separate dollar amounts. Box 12 has room for four coded entries; if your employer needs to report more, they’ll issue a second W-2 for the overflow.⁴

Catch-up contributions don’t get their own code. If you’re 50 or older, your regular deferrals and catch-up amounts are combined into a single Code D or Code AA figure.⁴ For the breakdown between regular and catch-up, check your pay stubs or plan statements.

You don’t report Code D or Code AA amounts separately on your Form 1040. The information flows from the W-2 into your return. The IRS uses the combined Code D and Code AA total to check whether you stayed under the annual deferral limit.

What the 2026 Limits Look Like on Your W-2

For 2026, the maximum elective deferral to a 401(k) is $24,500. That ceiling covers the combined total of traditional and Roth deferrals across every 401(k) plan you participated in during the year. If you switched jobs, both employers’ plans count against the same limit.⁵

Older workers get extra room:

Age 50 and older: an additional $8,000 in catch-up contributions, for a total possible deferral of $32,500.
Ages 60 through 63: a higher catch-up of $11,250 instead of $8,000, for a maximum of $35,750. This higher catch-up was created by the SECURE 2.0 Act and applies starting in 2025.⁵

So if you’re 62 and maxed out a traditional 401(k), Code D would show $35,750 as a single figure with no line item breaking out the catch-up.

If Code D and Code AA Add Up to More Than the Limit

This happens most often when you contributed to two employers’ plans in the same year. The excess deferral, plus any earnings on it, must be returned to you by April 15 of the following year. You need to contact your plan administrator to request the corrective distribution.⁶ Miss that April 15 deadline, and the excess is taxed twice: once in the year you contributed, again when you eventually withdraw. Your original W-2 doesn’t get corrected either way; it reflects what you actually deferred.

The Box 13 Retirement Plan Checkbox

Look at Box 13. There’s a small checkbox labeled “Retirement plan” that your employer checks if you were an active participant in a workplace retirement plan during the year. For a 401(k), that means you were credited with any contributions or forfeitures.⁷

The checkbox doesn’t change your 401(k) reporting, but it controls whether you can deduct contributions to a separate traditional IRA. When the box is checked, income-based phase-outs may reduce or eliminate that deduction. For 2026:⁵

Single filers covered by a workplace plan: $81,000 to $91,000 modified adjusted gross income.
Married filing jointly, contributing spouse covered: $129,000 to $149,000.
Married filing jointly, contributing spouse not covered but other spouse is: $242,000 to $252,000.
Married filing separately, covered by a plan: $0 to $10,000.

A checkbox marked when you weren’t an active participant can cost you an IRA deduction you’re entitled to. An unchecked box when you were an active participant can lead to claiming a deduction the IRS will later disallow.

Your Employer’s Match Won’t Appear on the W-2

Employer matching and profit-sharing contributions don’t show up anywhere on your W-2. They aren’t taxable to you when they’re made, so they’re excluded from Boxes 1, 3, and 5, and they don’t get a Box 12 code. For the match figure, check your plan statement or annual benefits summary.

SECURE 2.0 also lets employers make matching contributions directly into your Roth account. Even then, the employer match doesn’t land on your W-2. Roth employer matching contributions are reported on a Form 1099-R for the year they’re allocated to your account, using code G in Box 7.⁸ If your employer offers Roth matching, expect both a W-2 (for your own deferrals) and a 1099-R (for the match) at tax time.

How to Check Your W-2 Against Your Records

Pull your final pay stub for the year. Add up the year-to-date 401(k) deferrals and match that total to the Code D or Code AA figure in Box 12. Then check that Box 1 equals your gross wages minus pre-tax 401(k) deferrals, health insurance premiums, and any other pre-tax deductions. Box 3 and Box 5 should be higher than Box 1 by roughly the amount of your pre-tax 401(k) contributions.

Common errors: the wrong Box 12 code (for example, 403(b) deferrals reported under Code D instead of Code E), a missed check in Box 13, or pre-tax 401(k) deferrals mistakenly left in Box 1, which inflates your taxable income.⁷

If a number is wrong, start with your employer’s payroll department. They can issue a Form W-2c to correct it.⁹ If the correction arrives after you’ve already filed, you’ll need to submit an amended return on Form 1040-X along with the W-2c.

1
Internal Revenue Service. Topic No. 424, 401(k) Plans
2
Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates
3
Internal Revenue Service. Retirement Plans FAQs on Designated Roth Accounts
4
Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3
5
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
6
Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan
7
Internal Revenue Service. Common Errors on Form W-2 Codes for Retirement Plans
8
Internal Revenue Service. SECURE 2.0 Act Impacts How Businesses Complete Forms W-2
9
Internal Revenue Service. Form W-2c (Rev. January 2026) Corrected Wage and Tax Statement