Tax Withholding and the W-4: Get It Right in 2025

What withholding is — and isn't

Withholding is the money your employer removes from each paycheck and sends to the IRS on your behalf as a prepayment of your annual tax. It is not a separate tax; it is an installment plan. Get it right and your April bill lands near zero. Get it wrong and you either owe a surprise balance or hand the government an interest-free loan you reclaim as a refund.

The W-4 controls the dial

Your IRS — About Form W-4, Employee's Withholding Certificate tells your employer how much to withhold. The redesigned form no longer uses “allowances”; instead you report multiple jobs, dependents, and other income directly. Update it whenever your life changes — marriage, a new baby, a second job, or a working spouse — because those events move your true tax up or down.

Use the IRS estimator, not guesswork

The free IRS — Tax Withholding Estimator walks through your pay stubs and projects your year-end result, then tells you exactly how to adjust your W-4. Running it mid-year — especially after a raise or a job change — is the most reliable way to avoid both surprise bills and oversized refunds.

Withholding isn't only income tax

Your paycheck also withholds Social Security and Medicare (FICA) at fixed rates, separate from federal income tax. The IRS Topic No. 751, Social Security and Medicare Withholding Rates confirms the 6.2% Social Security rate (up to the annual wage base) and 1.45% Medicare rate that employees pay, matched by employers.

Covering side income through your W-4

If you have freelance income but also a W-2 job, you can ask for extra withholding on line 4(c) of the W-4 instead of making quarterly estimated payments. Many people find one lever simpler than two.