TL;DR
- ✅ You owe because withholding was lower than your tax, not because you did something wrong
- ✅ Measure the gap, then divide it by the paychecks you have left
- ✅ Put that amount in Step 4(c), or complete Step 2 for a second income
- ✅ The earlier in the year you fix it, the smaller the per-paycheck cost
Step 1: find out why you owe
Second job or working spouse
Each employer withholds as if it is your only income. Fix with Step 2. See the two-jobs and married guides.
Side income or freelance work
No tax is withheld on it. Cover it through Step 4(c) on your W-2 job, or with quarterly estimates.
A raise, bonus or new job
Your W-4 was built for the old pay. Bonuses are often withheld at a flat 22 percent.
Life changes
Marriage, divorce, a child, or a child aging out of the credit change the right amount of withholding.
Interest, dividends or retirement income
No withholding unless you request it. Use Step 4(a), or Step 4(c) for the tax on it.
Step 2: measure the gap
Look at your last pay stub: year-to-date federal income tax withheld and gross pay. Divide withholding by gross pay to see your effective withholding rate, then compare it with the effective rate on last year’s return (total tax divided by gross income). If last year’s rate was higher than this year’s withholding rate, you are heading for a bill. The calculator below does the projection for you.
Find your shortfall and the exact W-4 fix — free
Enter your pay and what you have withheld so far to see what to change.
Open the W-4 Calculator →Step 3: pick the fix
- Flat extra amount. Shortfall ÷ paychecks left, entered in Step 4(c). See the Step 4(c) guide.
- Another income in the household. Complete Step 2 on both W-4s; see W-4 with two jobs and married couples who both work.
- Side income. Add its estimated tax per paycheck in 4(c); see W-4 with freelance income.
⚠️ Late in the year
With only a few paychecks left, the per-paycheck number can be large. Withholding is generally treated as paid evenly through the year, so a late increase can still cover a shortfall for penalty purposes. If it is too large, a one-time estimated payment is an alternative. Check the safe harbor rules.
Step 4: submit the form and verify
Give the new W-4 to your payroll department. Check your next two pay stubs: federal withholding should rise by about the amount you entered. If you want to double-check the approach before changing anything, read refund vs. adjusting your W-4.
Frequently asked questions
Why do I owe taxes when I have always gotten a refund?
Common causes are a second job or a working spouse, side income with no tax withheld, a raise or bonus, a child aging out of the child tax credit, or a W-4 that was set up before your situation changed. Withholding follows what is on your W-4, not what you will actually owe.
How do I stop owing taxes on my next paycheck?
Submit a new W-4 to your employer. Add the missing amount to Step 4(c) as a flat dollar figure per paycheck, or complete Step 2 if you have another job or a working spouse. Most employers apply it within one or two pay periods.
How much extra should I withhold?
Take what you expect to owe at year end and divide by the paychecks left. For example, $1,500 with 15 paychecks left is $100 per paycheck. The Step 4(c) guide has more examples.
Do bonuses cause me to owe?
Often not by themselves. Many employers withhold a flat 22 percent on bonuses, which may be lower than your actual marginal rate if you earn a lot. If your bonus pushes you into a higher bracket, you may owe the difference.
Can I get a penalty for not withholding enough?
Yes, if your withholding and estimated payments are below the safe harbor: 90 percent of this year’s tax or 100 percent of last year’s (110 percent if your income was above $150,000). Owing a small amount does not trigger the penalty, but a large shortfall can.
Key terms in this article
Related guides
W-4 Step 4(c): How Much Extra Withholding to Enter (2026)
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Tax Refund vs. Adjusting Your W-4: How to Keep More Money Every Paycheck
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