What goes on a W-4 and why it matters

A W-4 is the form you give your employer to tell them how much federal income tax to take out of your paycheck. Your employer sends that withheld money to the IRS on your behalf. If you fill it out wrong, you might have too much taken (and get a refund later) or too little taken (and owe money when you file your tax return).

The W-4 has changed since 2020. The old version had worksheets and allowances. The new version asks you directly about your life: Do you have a second job? Are you married? Do you have kids? Based on your answers, it calculates a number that tells your payroll department how much to withhold.

You fill out a W-4 when you start a new job. You can also fill out a new one anytime your situation changes — if you get married, have a child, buy a house, or get a second job. Your employer must have a completed W-4 on file before they can pay you.

Key Takeaways

  • You must complete a W-4 before your first paycheck; your employer cannot pay you without one on file.
  • The form asks about your filing status, dependents, and other income sources so the IRS can calculate the right withholding amount.
  • If you have a spouse who also works, you and your spouse should coordinate your W-4s to avoid withholding too much or too little.
  • You can change your W-4 anytime your situation changes, such as getting married, having a child, or taking a second job.

Step 1: Fill in your name, address, and Social Security number

At the top of the form, write your full legal name, home address, and nine-digit Social Security number. Use the name and SSN that match your Social Security card — this is how the IRS links your withholding to your tax record.

Your employer also needs this information to report your wages to the IRS at the end of the year on a W-2 form. If your name or SSN is wrong on the W-4, your W-2 will be wrong too, and that can delay your tax refund or cause IRS notices.

Step 2: Choose your filing status

Check one box: Single, Married Filing Jointly, Married Filing Separately, or Head of Household. Use the status you expect to have on December 31 of that tax year — not your status today.

Your filing status tells your employer how much of your income is taxable. Single people and married people filing separately have less of their income taxed before withholding starts, so more is withheld. Married filing jointly and head of household have more income before withholding kicks in, so less is withheld per paycheck.

If you are not sure which status fits you, the IRS has a tool on irs.gov called the Filing Status tool. Head of Household applies if you pay more than half the household expenses and live with a dependent who is not your spouse.

Step 3: Claim your dependents

A dependent is usually your child under age 17, or an adult (like a parent) you support financially. For each dependent, you get a credit that reduces your federal tax. Your W-4 uses this to lower your withholding.

Write the number of dependents you claim in the box labeled "Dependents." This is not the same as the number of children you have — only count people you actually support and who live with you (with rare exceptions for parents or relatives). If you claim dependents you do not actually support, you will owe money at tax time and may face penalties.

If you are not sure whether someone counts as your dependent, the IRS website has a Dependent Exemption tool. You can also ask a tax professional or your employer's HR department.

Step 4: Account for other income and multiple jobs

If you have a second job, your spouse works, or you have income from self-employment, rental property, or investments, you need to tell your employer. The reason: withholding is calculated based on the assumption that this job is your only income. If you have other income, you might not have enough withheld across all your jobs combined.

The W-4 has a section for this. If you have a spouse who works, you and your spouse should coordinate your W-4s. One common approach is to have the higher earner claim most or all of the dependents, and the lower earner claim none. This spreads the withholding more evenly across both paychecks.

If you have a second job or self-employment income, you can either have extra money withheld from this job, or you can use the IRS withholding calculator at irs.gov to figure out the right amount and enter it in the "Other Income" section of the form.

Step 5: Claim credits and adjustments (if any)

The W-4 has a section for tax credits and deductions. Most people leave this blank. You only fill it in if you have specific credits the standard calculation does not account for — such as child care expenses, education credits, or significant itemized deductions.

If you are not sure whether you have credits or deductions that belong here, use the IRS withholding calculator at irs.gov/taxes/individuals/tax-withholding-estimator. It walks you through your situation and tells you whether you need to enter anything in this section. If you do not use the calculator and are not certain, leave it blank — it is safer to have a little extra withheld than to owe money at tax time.

Step 6: Sign and date the form

At the bottom of the W-4, sign and date the form. Your signature tells your employer that the information is correct and that you understand the consequences of claiming dependents you do not actually support.

Give the completed form to your employer's HR or payroll department. Keep a copy for your records. Your employer must have it on file before your first paycheck is processed.

What happens after you submit your W-4

Your employer sends your W-4 information to their payroll system. Starting with your next paycheck, the withholding amount changes based on what you entered. You will not see a dramatic change in one paycheck — withholding is spread across the year — but over time you should see the right amount being taken out.

At the end of the year, your employer sends you a W-2 form showing how much you earned and how much was withheld. When you file your tax return, the IRS compares what was withheld to what you actually owe. If too much was withheld, you get a refund. If too little was withheld, you owe the difference.

If you realize you made a mistake on your W-4, or if your situation changes, you can fill out a new one anytime. There is no penalty for changing it. Just give the new form to your employer, and the new withholding takes effect on the next paycheck.

Frequently Asked Questions

Can I claim zero dependents if I have kids?

Yes. Claiming zero dependents means more money is withheld from each paycheck. Some people do this if they want a bigger refund, or if they are not sure how many dependents they can legally claim. You can always claim the actual number of dependents you support — the form asks for the truth, not a strategy.

What if I do not have a Social Security number yet?

You cannot start work without a valid SSN or an Individual Taxpayer Identification Number (ITIN). If you are waiting for your SSN, ask your employer's HR department whether you can start work and complete the W-4 once your number arrives. Some employers will not process payroll without it on file.

Do I need to fill out a new W-4 every year?

No. Your W-4 stays in effect until you change it or leave the job. You only need a new one if your situation changes — marriage, divorce, new dependents, second job, or if you want to adjust your withholding because you got a big refund or owed money last year.

What if my spouse and I both work and we do not coordinate our W-4s?

You might have too little withheld across both paychecks combined, even though each W-4 looks correct on its own. This happens because each employer calculates withholding as if that job is your only income. If you both work, one of you should claim fewer dependents or enter an amount in the "Other Income" section to make up the difference.

Can my employer refuse to accept my W-4?

No. Your employer must accept a completed W-4 and use it to calculate withholding. However, if the IRS suspects you are claiming false dependents to avoid withholding, they can contact your employer and require a different withholding amount. This is rare and usually only happens after an audit.