On Form 1040, only two W-2 numbers move over directly: Box 1 wages go on Line 1a, and Box 2 federal income tax withheld goes on Line 25a. Everything else on your W-2 either supports those figures, feeds a separate form, or is informational. That is the short version of how a W-2 connects to Form 1040, and for most wage earners it is the whole story.
Box 1 Wages Go on Line 1a
Box 1 reports your total taxable wages, tips, and other compensation for the year. It is usually smaller than your gross pay because pre-tax items like 401(k) deferrals and employer health premiums have already been subtracted. Copy the Box 1 figure onto Form 1040, Line 1a.1Internal Revenue Service. Form 1040
Worked more than one job? Add the Box 1 amounts from every W-2 you received and enter the combined total on Line 1a. Include short-term and part-time jobs. The IRS gets copies of all your W-2s, and a mismatch between what you report and what they already have is one of the fastest ways to get a notice.
Box 2 Federal Withholding Goes on Line 25a
Box 2 is the federal income tax your employer pulled from your paychecks over the year. It goes on Form 1040, Line 25a, in the Payments section near the bottom of the form.1Internal Revenue Service. Form 1040 Multiple W-2s? Combine the Box 2 amounts the same way you combined wages.
Line 25a is where the refund-or-balance-due math starts. Your total tax liability gets compared against your total payments, which include Line 25a withholding plus any estimated tax payments. If withholding exceeds your liability, you get a refund. If it falls short, you owe the difference.
From Line 1a to the Tax You Actually Owe
Line 1a is only the starting point. The 1040 adds any other income and above-the-line adjustments to reach adjusted gross income on Line 11, then subtracts either the standard deduction or Schedule A itemized deductions on Line 12e, producing taxable income on Line 15.1Internal Revenue Service. Form 1040
For the 2026 tax year, the standard deduction is $16,100 for single filers and married filing separately, $32,200 for married filing jointly and qualifying surviving spouses, and $24,150 for head of household.2Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Most filers with only W-2 income take the standard deduction, so the math is straightforward: Line 1a wages minus the standard deduction (plus any qualified business income deduction on Line 13) equals taxable income on Line 15. That taxable income is what the tax tables use to figure your actual tax.
Boxes 3 Through 6: Social Security and Medicare
Boxes 3 through 6 report Social Security and Medicare wages and the corresponding taxes withheld. None of these figures move to a line on the main Form 1040. They exist so the IRS and Social Security Administration can verify payroll tax withholding.
Box 3 shows wages subject to Social Security tax, capped at $184,500 for 2026.3Social Security Administration. What Is the Current Maximum Amount of Taxable Earnings for Social Security? Box 4 shows Social Security tax withheld at the 6.2% employee rate. Box 5 reports Medicare wages, which have no cap. Box 6 shows the 1.45% Medicare tax withheld.4Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates
Two situations pull these boxes into your return. If you earned more than $200,000, your employer should have withheld an additional 0.9% Medicare tax on wages above that threshold. You may need Form 8959 to reconcile the Additional Medicare Tax, particularly if your filing status changes the threshold (married filing jointly uses $250,000, and married filing separately uses $125,000).4Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates
The second situation catches people who changed jobs. If you had more than one employer and combined Box 3 wages topped $184,500, your total Box 4 Social Security tax withheld across all W-2s may exceed the annual maximum of $11,439 (6.2% of $184,500). Each employer withholds independently, so neither knows about the other. Claim the excess as a credit on Schedule 3 of your Form 1040. This is real money people leave on the table every year.
Box 10: Dependent Care Benefits
If your employer offers a dependent care flexible spending account, your contributions show up in Box 10. For 2026, up to $7,500 per household ($3,750 if married filing separately) can be excluded from income through these programs. Amounts within the exclusion are already left out of Box 1, so they do not increase your tax.
Received dependent care benefits? Complete Part III of Form 2441 to calculate whether any portion exceeds the exclusion and becomes taxable. Any taxable excess goes on Form 1040, Line 1e.5Internal Revenue Service. Instructions for Form 1040
Box 12 Codes Worth Knowing
Box 12 uses letter codes to report various types of compensation and benefits. Most do not go on the 1040 directly, but a few are worth recognizing.
Code D reports your elective deferrals to an employer-sponsored 401(k) plan. Those contributions are already excluded from Box 1, so you do not enter them separately. If your total deferrals across all employers exceeded $24,500 for 2026, though, the excess must be reported as income on Line 1h.6Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs
Code DD reports the total cost of employer-sponsored health coverage, including both the employer’s share and yours. It is purely informational and has no effect on your taxes or your 1040.7Internal Revenue Service. Form W-2 Reporting of Employer-Sponsored Health Coverage
Code W reports employer contributions (including pre-tax payroll deductions) to your Health Savings Account. Those flow to Form 8889, not to the 1040’s income lines.
If your Box 12 shows Code D and Box 13 has the Retirement plan box checked, that also affects whether you can deduct traditional IRA contributions. The deduction phases out at lower income levels when you are covered by a workplace retirement plan.
Box 14: A Catch-All
Box 14 is where employers report items that do not fit elsewhere. Common entries include state disability insurance taxes, union dues, uniform payments, and educational assistance. Starting with the 2026 W-2, the IRS split this into Box 14a (labeled “Other”) and Box 14b (for a new Treasury Tipped Occupation Code used when cash tips are reported).8Internal Revenue Service. General Instructions for Forms W-2 and W-3
Whether a Box 14 item affects your 1040 depends entirely on what it is. State disability insurance withholding may be deductible on your state return but not your federal one. Union dues generally are not deductible on federal returns. If you see an unfamiliar entry, ask your employer’s payroll department for an explanation before deciding it does not matter.
Boxes 15 Through 20: State and Local, Not Federal
Boxes 15 through 20 cover state and local wage and tax information. Box 16 shows wages subject to state income tax, Box 17 shows state tax withheld, and Boxes 18 through 20 do the same for local taxes. None of these go on your federal Form 1040. They are for your state and local returns. If you live in a state with no income tax, expect these boxes to be blank.
If Your W-2 Is Missing or Wrong
Employers must provide your W-2 by January 31. If that date falls on a weekend, the deadline shifts to the next business day. When yours does not show up or contains errors, the IRS recommends a three-step process.9Internal Revenue Service. If You Don’t Get a W-2 or Your W-2 Is Wrong
Start with your employer. Reach out to payroll or HR to confirm the W-2 was sent or made available electronically, and verify that your name, address, and Social Security number are correct in their system. If you still have not received it by the end of February, call the IRS at 800-829-1040. Have your employer’s name, address, and phone number ready, along with the dates you worked there; the IRS will contact the employer on your behalf. As a last resort with the filing deadline approaching, use your final pay stub to estimate wages and withholding, then attach Form 4852 to your return as a substitute for the W-2.10Internal Revenue Service. About Form 4852, Substitute for Form W-2
If you filed with Form 4852 and later receive an actual W-2 showing different amounts, file an amended return on Form 1040-X to correct the discrepancy.11Internal Revenue Service. W-2 – Additional, Incorrect, Lost, Non-Receipt, Omitted