Every time you get a paycheck, your employer holds back part of your wages and sends it to the IRS. That money is called federal withholding. Think of it as paying your taxes a little at a time throughout the year, instead of writing one big check in April.
The key thing to understand: withholding is not the tax itself. It is your best guess at what you will owe. When you file your return, the IRS works out what you actually owe from your total income, deductions and credits. Then one of two things happens:
- Too much was withheld: you get a refund of the extra you paid during the year.
- Too little was withheld: you owe the difference in April.
Why some people owe money at tax time
Almost always, the W-4 was set up in a way that no longer matches real life. The most common reasons:
- Two jobs, but each W-4 only accounts for one. Each employer withholds as if its job is your only income. Combined, your income lands in a higher bracket. If Job 1 pays $40,000 and Job 2 pays $25,000, you are taxed on $65,000, but each employer withheld as if you earned $40,000 or $25,000 alone.
- You got married and never updated your W-4. Two incomes on a joint return can push you into a higher bracket than either W-4 assumes.
- You claimed dependents or deductions you don't actually qualify for. Every one you claim lowers withholding, so overclaiming leaves you short.
- You have freelance or side income. Nobody withholds on it. Earn $10,000 on the side without quarterly payments and the tax, plus possible penalties, is due all at once.
- A big bonus or stock payout. Bonuses are often withheld at a flat 22%. If your real rate is higher, you make up the difference in April.
A real-world W-4 mistake: Maria earns $50,000 at her full-time job and $8,000 in tips waitressing on weekends. Years ago she marked "Exempt" on the restaurant W-4 and never changed it, so no income tax comes out of that paycheck. At tax time she owes income tax on that job's pay, plus Social Security and Medicare on any tips that weren't run through payroll.
The new tips deduction helps: she can deduct qualified tips (up to $25,000, for 2025 through 2028), which lowers her federal income tax. Tips are still subject to Social Security and Medicare, and she should update her W-4 so her withholding matches her real situation.
How your employer knows how much to withhold
You tell them on Form W-4: your filing status, other jobs or income, dependents, and any extra amount you want withheld. Your employer runs that through the IRS withholding tables. The free IRS Tax Withholding Estimator takes about 10 minutes and tells you whether you are on track.
W-4 changes worth making now
The One Big Beautiful Bill Act added deductions that lower taxable income for many workers:
- Qualified tips: deduct up to $25,000 (employees and qualifying self-employed, 2025 through 2028).
- Qualified overtime: deduct the "half" premium part of required overtime pay, up to $12,500 ($25,000 joint), phasing out above $150,000 of income ($300,000 joint), 2025 through 2028.
These are deductions, not exclusions. Your employer may still withhold on the full amount, so you may be over-withheld. We can help you adjust your W-4 so the money stays in your paycheck instead.
IRS resources
- Form W-4: give an updated copy to your employer.
- Tax Withholding Estimator: free, about 10 minutes.
Bottom line: A big refund feels great, but it means the IRS held your money interest-free all year. Owing feels terrible, but it means you kept more in your pocket. The goal is to land close to zero, and that starts with a correct W-4.
General education only, not advice for your specific situation. Figures checked October 2026. Tax law changes, so confirm current figures at IRS.gov or ask us.