What goes on a W-4 and why it matters

A W-4 form tells your employer how much federal income tax to withhold from your paycheck. The more you claim, the less tax comes out each pay period — but you might owe money at tax time. The fewer you claim, the more comes out now — but you might get a refund. The form has five main sections: your name and address, your filing status, your dependents, your jobs and income, and any extra withholding you want.

You fill out a W-4 when you start a new job, and you can fill out a new one anytime your situation changes — a marriage, a child, a second job, or a big change in income. Your employer sends the information to the IRS, and the IRS uses it to track whether you're on pace to owe or to receive a refund.

Key Takeaways

  • Step 1 is your personal information; Step 2 is your filing status (single, married, head of household); Step 3 is dependents you claim.
  • Step 4 asks about other jobs or income — if you have a spouse who works or a second job yourself, you must complete this section or you will have too little withheld.
  • Step 5 lets you ask your employer to withhold extra money each paycheck if you expect to owe at tax time.
  • If nothing in your life has changed since you last filled one out, you can often leave most sections blank and just sign it.
  • The IRS website has a withholding calculator that shows you what to enter in Step 4 if you have multiple jobs or a working spouse.

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

Write your full legal name as it appears on your Social Security card. Print clearly or type. Enter your home address and your Social Security number. If you have moved since your last job, use your current address. Your employer uses this section to report your income to the IRS under your name and number.

If your name has changed — through marriage, divorce, or legal name change — make sure it matches what the Social Security Administration has on file. If it does not, contact Social Security before you start the job, or your W-2 at the end of the year will not match your tax return and the IRS will flag it.

Step 2: Choose your filing status

Check one box: Single, Married Filing Jointly, Married Filing Separately, or Head of Household. Your filing status determines your tax brackets and standard deduction. Use the status you plan to file under on your tax return in April, not your current marital status on the day you fill out the form.

If you are married and both you and your spouse work, you can both claim "Married Filing Jointly" — but you must complete Step 4 on both forms, or too little tax will be withheld from your combined paychecks. Head of Household applies if you are unmarried and pay more than half the household expenses for yourself and a dependent.

Step 3: Claim your dependents

Enter the number of children under 17 and the number of other dependents you claim on your tax return. A dependent is usually a child, stepchild, or relative you support and who lives with you for more than half the year. Do not count yourself or your spouse. Each dependent reduces the tax withheld from your paycheck.

If you are unsure whether someone counts as your dependent, the IRS website has a tool that walks you through the rules. If you claim a dependent on your W-4 but do not claim them on your tax return in April, the IRS will recalculate and you will owe the difference. Only enter dependents you are certain about.

Step 4: Account for multiple jobs or a working spouse

This is the section most people skip — and most people get wrong. If you have two jobs, or if you are married and your spouse works, you must complete Step 4 or your withholding will be too low and you will owe money in April.

The form gives you two paths. The first is to use the IRS withholding calculator at irs.gov/taxes/individuals/tax-withholding-estimator. You enter your income from all jobs, your filing status, and your dependents, and the calculator tells you what to enter on line 4c. The second path is to use the worksheet printed on the back of the form, which does the same math by hand.

If you use the calculator and it tells you to enter zero on line 4c, enter zero — do not leave it blank. If you have a second job that is seasonal or temporary, you can fill out a new W-4 when that job ends to adjust your withholding back down.

Step 5: Request extra withholding if you want it

Line 4d lets you ask your employer to withhold an extra dollar amount from each paycheck — $10, $50, $100, whatever you choose. Use this if you know you will owe money at tax time and you want to pay it gradually through your paychecks instead of in a lump sum in April. You might use this if you have self-employment income, rental income, or investment income that is not subject to withholding.

You can change this amount anytime by filling out a new W-4. If you ask for $50 extra per paycheck and later realize you do not need it, fill out a new form and change it to zero.

Sign and date, then give it to your employer

Sign and date the form at the bottom. Your employer will keep it on file and use it to calculate your withholding starting with your next paycheck. You do not send it to the IRS — your employer does. Keep a copy for your records.

If you fill out a new W-4 during the year, your employer will start using the new withholding amount within one to two pay periods. The old withholding stops and the new one begins. If you are owed a refund from the old withholding, you will not see it until you file your tax return — your employer does not refund the difference.

Frequently Asked Questions

What if I do not know my filing status yet?

Use the status you expect to have on December 31 of that tax year. If you are getting married in November, use "Married Filing Jointly" on your W-4 now. If you are unsure, use "Single" for now and fill out a new W-4 once your situation is certain. You can update it anytime.

Do I have to fill out Step 4 if I only have one job?

Only if your spouse works or you have other income. If you have one W-2 job, no spouse, and no other income, you can leave Step 4 blank. If you have a spouse who works, both of you must complete Step 4 or your combined withholding will be wrong.

What happens if I claim too many dependents on my W-4?

Too little tax will be withheld from your paycheck, and you will owe money when you file your tax return in April. The IRS may also charge a penalty if you underpaid by a large amount. Only claim dependents you actually claim on your tax return.

Can I claim zero dependents to get a bigger refund?

Yes, but that is not how withholding works. Claiming zero dependents just means more tax comes out of your paycheck now. You will not get a bigger refund — you will just have overpaid throughout the year. Claim the dependents you actually have, and use Step 5 if you want extra withholding.

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

No. You only need a new W-4 if something changes — your filing status, your dependents, a new job, or a big change in income. If nothing has changed, your old W-4 stays in effect. However, the IRS recommends reviewing your withholding each year to make sure it is still correct.