The short answer
Federal income tax taken out of your paychecks is withholding — a prepayment of your tax. You owe at filing time when your withholding (plus any credits and payments) is less than your actual tax for the year. That usually means your Form W-4 no longer matches your situation, or you had income with no withholding. You can fix it for the future by checking your withholding with the IRS Tax Withholding Estimator and giving your employer a new Form W-4.
If you need to pay this year's balance, see I can't pay my tax bill.
How withholding works
- Your employer figures withholding from the Form W-4 you gave it. Box 2 of your W-2 shows the total federal income tax withheld for the year.
- You give the W-4 to your employer, not the IRS.
- If you never gave your employer a W-4, it generally withholds as if you were single (or married filing separately) with no other adjustments.
Common reasons you owe
| Reason | Why withholding falls short | Where the W-4 addresses it |
|---|---|---|
| Two jobs, or both spouses work | Each employer withholds as if its job were your only income | Step 2 |
| Dependents or credits changed | A child aged out or a credit no longer applies | Step 3 |
| Income with no withholding | Interest, dividends, investment gains, or retirement income | Step 4(a), or estimated payments |
| Self-employment income | Freelance or other self-employment income (also subject to self-employment tax) | Tax Withholding Estimator (Step 2(a)), or estimated payments |
| Deductions changed | You stopped itemizing or expected deductions did not happen | Step 4(b) |
| Bonus or supplemental pay | Often withheld at a flat 22%, which may not match your rate | Step 4(c) extra withholding |
| Raise or mid-year job change | Old W-4 information no longer fits your income | A new W-4 |
Bonuses and the flat 22%
Employers often withhold federal income tax on bonuses and other supplemental wages at an optional flat 22%. Once an employee's supplemental wages from an employer exceed $1 million in a calendar year, Publication 15 (2026) requires the excess to be withheld at a mandatory 37%, regardless of the employee's Form W-4. This is a withholding rate, not the tax rate on your bonus — your actual tax is figured on your total income when you file.
How to fix it for next year
- Use the IRS Tax Withholding Estimator on IRS.gov with a recent pay stub and your latest tax return. The IRS updated it in 2026 to reflect the 2025 tax law changes.
- Complete a new Form W-4 based on the results and give it to your employer's payroll department.
- Check again after big changes: marriage or divorce, a new child, a second job, a spouse starting work, or new side income.
The 2026 Form W-4 was updated so employees can account for new federal deductions under the 2025 tax law — such as those for qualified tips, overtime pay, and passenger vehicle loan interest — through the Step 4(b) Deductions Worksheet. Each deduction has its own eligibility rules and limits — see No Tax on Tips, No Tax on Overtime, and the 2025 tax law overview.
Withholding vs. estimated tax
If you have significant income with no withholding — rental or investment income, for example — you can raise your W-4 withholding (Step 4(a) or 4(c)) or make estimated tax payments. Form W-4 says not to include self-employment income in Step 4(a); if you have self-employment income, it tells you to use the Tax Withholding Estimator, or you can make estimated tax payments. Publication 505 explains when estimated tax is required. See Quarterly estimated taxes.
Example (illustrative)
Ana and Leo each earn about $70,000 at separate jobs and file jointly. In this example, both completed their W-4s as married filing jointly and neither accounted for the other job in Step 2. Each employer therefore withholds as if that salary were the household's only income, so together they are under-withheld and owe at filing time. Not every married couple with two jobs will owe — the result depends on how each W-4 is completed and on the household's actual income, deductions, and credits. Using the Tax Withholding Estimator, they complete new W-4s that account for both jobs (Step 2), and their withholding rises for the following year.
Common myths
- "A refund means I paid less tax." A refund only means you overpaid during the year.
- "Owing means I made a mistake on my return." Usually it means withholding was too low, not that the return is wrong.
- "A new W-4 guarantees I won't owe." It only changes future withholding; your actual income and credits decide the result.