401(k) contributions do not get their own line on Form 1040. Traditional (pre-tax) deferrals are already subtracted from the wages your employer reports in Box 1 of your W-2, and Roth 401(k) deferrals are already included in that same Box 1 figure because they came out of after-tax pay. Either way, you copy Box 1 to Form 1040, Line 1a, and the 401(k) side of things is done. The real reporting happens on the W-2 itself.1Internal Revenue Service. Topic No. 424, 401(k) Plans
Why There’s No Separate 401(k) Line on Form 1040
Look at your W-2. Box 1 (Wages, Tips, Other Compensation) is your income after pre-tax 401(k) deferrals have been removed, which is why it’s often lower than your gross salary. Box 3 (Social Security Wages) and Box 5 (Medicare Wages) still contain those deferrals, because 401(k) money is exempt from federal income tax but not from FICA.1Internal Revenue Service. Topic No. 424, 401(k) Plans If the gap between Box 1 and Box 5 lines up with what you contributed, the payroll math is right.
Box 12 itemizes the exact deferral amount using a letter code:
- Code D for pre-tax (Traditional) 401(k) deferrals, including any catch-up.
- Code AA for designated Roth 401(k) contributions, including Roth catch-up.
The IRS tells employers to fold catch-up contributions into the same code as the regular deferral rather than break them out on a separate line, so a worker age 50 or older will see one combined number.2Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3 – Section: Box 12 Codes If you contributed to both types in the same year, both codes will appear.
Tax software imports Code D and Code AA when you enter the W-2, but only for checks like verifying you stayed under the annual limit. Neither code creates a deduction on the 1040.
Traditional (Pre-Tax) 401(k) Contributions
If your contributions were pre-tax, there is nothing to add to your return. The deduction is already inside the Box 1 number.1Internal Revenue Service. Topic No. 424, 401(k) Plans You enter Box 1 on Form 1040, Line 1a, and move on.3Internal Revenue Service. Form 1040 U.S. Individual Income Tax Return
Pre-tax 401(k) deferrals are not an adjustment on Schedule 1 and not an itemized deduction on Schedule A. Claiming them a second time would double-count the tax break, and the IRS can spot the discrepancy by comparing your Box 1 wages to the Code D amount.
Filers 65 and older can use Form 1040-SR instead. The line numbering is the same: Box 1 to Line 1a.1Internal Revenue Service. Topic No. 424, 401(k) Plans
Roth 401(k) Contributions
Roth 401(k) money came out of after-tax pay, so it’s already sitting inside Box 1. Same move: Box 1 to Form 1040, Line 1a.3Internal Revenue Service. Form 1040 U.S. Individual Income Tax Return No deduction and no adjustment, because you’re paying tax on this money now in exchange for tax-free qualified withdrawals later.
The Code AA figure in Box 12 is informational. It tells the IRS the contribution was properly taxed in the current year so it won’t be taxed again when you withdraw it in retirement.
What About the Employer Match?
Employer matching contributions do not appear on your W-2 and do not go anywhere on your 1040. The match goes straight into the plan and is not part of your taxable wages, so it isn’t in Box 1, isn’t in Box 12, and isn’t your problem to report.
Where a 401(k) Actually Creates a 1040 Entry: The Saver’s Credit
The one place a 401(k) contribution shows up on the 1040 beyond Line 1a is the Retirement Savings Contributions Credit, better known as the Saver’s Credit. It’s a dollar-for-dollar reduction in tax owed, and it applies to Traditional and Roth 401(k) contributions alike.4Internal Revenue Service. Retirement Savings Contributions Credit (Savers Credit)
To qualify, you must be at least 18, not a full-time student, and not claimed as a dependent. The credit is worth 50%, 20%, or 10% of up to $2,000 in contributions ($4,000 if married filing jointly), depending on your adjusted gross income from Line 11. Maximum credit: $1,000 single, $2,000 joint. For 2026, the credit phases out entirely above $80,500 (joint), $60,375 (head of household), and $40,250 (single).5Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
You calculate the credit on Form 8880.6Internal Revenue Service. Form 8880 Credit for Qualified Retirement Savings Contributions The result flows to Schedule 3, Line 4. The Schedule 3 total on Line 8 then carries to Form 1040, Line 20.7Internal Revenue Service. 2025 Schedule 3 (Form 1040)
Excess Deferrals: The One Situation That Forces an Adjustment
If your combined 401(k) deferrals across all employers exceed the annual limit ($24,500 for 2026, higher with catch-up), you need to pull the excess out of the plan, along with any earnings on it, by April 15 of the following year.8Internal Revenue Service. 401(k) Plan Fix-It Guide – Elective Deferrals Werent Limited to the Amounts Under IRC Section 402(g) Miss that deadline and the same money is taxed twice: once now and again when eventually distributed.
When the correction happens on time, the excess must be included in wages for the year of the deferral. For pre-tax excess deferrals, that means adding the excess to your Line 1a wages if Box 1 didn’t already capture it. The plan will send a Form 1099-R for the corrective distribution, typically with Code 8 or Code P in Box 7.9Internal Revenue Service. Instructions for Forms 1099-R and 5498 Any earnings distributed with the excess are taxable in the year of the distribution.
This usually happens after a mid-year job change, because neither employer sees what you contributed at the other. Catching the overage before April 15 is on you.