Check how much tax is withheld from your pay

Your employer takes tax out of every paycheck and sends it to the IRS on your behalf. How much they take is decided entirely by a form you filled in on your first day, usually in a hurry and often wrongly. Nobody checks it for you, and the error only surfaces the following April.

The form

W-4, given to your employer — not to the IRS

Check it

In January, and after any change in job, pay or family

Tool

The IRS withholding estimator, about 25 minutes

Cost to change

Nothing, and you can change it as often as you like

What withholding is for

The United States collects income tax as you earn rather than in a lump sum. Each payday your employer withholds an estimate of what you will owe. When you file a return the following spring, the estimate is reconciled against your actual liability: withhold too little and you owe the difference, withhold too much and you get a refund.

The goal is to land close to zero either way.

When to check it

The IRS recommends checking every January. Check it again straight away after any of these:

• Starting a job, or starting a second one
• A raise, a bonus, or a long period of unpaid leave
• Marriage, divorce, or a child being born or adopted
• A spouse starting or stopping work
• Income that has no withholding at all — freelance work, gig platforms, rental income, interest

Two jobs is the classic trap. Each employer withholds as though its salary is your only income, so both apply the low rates at the bottom of the scale and the combined total falls short.

Using the estimator

The IRS runs a free withholding estimator. Have your most recent pay stubs from every job, your spouse's if you file jointly, and last year's tax return if you had other income. It asks nothing that identifies you and saves nothing.

The output is an estimate of where you will land and, if you want it, a pre-filled W-4 to hand to your employer. Give the new form to your employer's payroll or HR — the IRS never receives it. Then check one or two paychecks later that the change actually took effect.

Reading your pay stub

Every stub separates gross pay from what was taken out. Expect to see federal income tax, Social Security and Medicare (together labelled FICA), usually state income tax, and sometimes local tax.

Social Security and Medicare are fixed percentages and are not affected by your W-4 — only the federal and state income tax lines are. Some visa categories are exempt from FICA entirely; if you believe you are and it is still being deducted, raise it with payroll early, because recovering it later is slow.

If too little was withheld and you end the year owing more than you can pay at once, that is a solvable problem — see what to do if you owe tax and cannot pay.