What the W-4 form does and why you fill it out

The W-4 is the form you give your employer to tell them how much federal income tax to withhold from your paychecks. Your employer sends that withheld money to the IRS on your behalf. If you withhold too little, you'll owe money when you file your tax return. If you withhold too much, you'll get a refund — but you're essentially giving the government an interest-free loan all year.

You fill out a new W-4 when you start a job, and you can change it anytime your situation changes — a marriage, a second job, a child, or a major change in income. The form itself has changed several times; the current version (released in 2020) is simpler than older versions but works differently, so old instructions won't match what you see.

Key Takeaways

  • The W-4 has five main sections: personal information, filing status, jobs and income, deductions and credits, and other income — you only fill in the parts that apply to you.
  • Your filing status (single, married, head of household) is the single biggest factor in how much tax is withheld, and changing it changes your withholding immediately.
  • If you have only one job and claim the standard deduction, you can often stop after Step 1 and leave the rest blank.
  • The IRS provides a tax withholding calculator on its website that can tell you whether your current withholding is roughly correct.
  • You do not need to file a new W-4 every year — only when your situation changes or when you want to adjust your withholding.

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

This section is straightforward. Print your full legal name, current address, and nine-digit Social Security number. Make sure the name matches what's on your Social Security card — if it doesn't, contact Social Security to update it before you submit the W-4.

Your employer uses this information to report your wages to the IRS. If your address changes later, you can update it with your employer without filing a new W-4.

Step 2: Select your filing status

Your filing status determines the tax brackets and standard deduction you'll use when you file your return. It also determines how much tax your employer withholds. The five options are: Single, Married Filing Jointly, Married Filing Separately, Head of Household, and may have access to Widow(er).

Use the status you expect to have on December 31 of the tax year. If you're married but file separately, each spouse fills out their own W-4 with "Married Filing Separately" selected. If you're single with dependents and pay more than half the household expenses, you may be able to claim Head of Household, which gives you a larger standard deduction than Single.

This is the most important choice on the form. Changing your filing status changes your withholding significantly, so if you got married, divorced, or had a major life change, update this first.

Step 3: Claim dependents and other credits

In this step, you list dependents (children or other people you support) and claim certain tax credits. The form asks you to enter the number of dependents you claim, and it calculates a withholding reduction based on that number.

You can claim a dependent on your W-4 only if that person is also claimed on your tax return. Common dependents are children under 17 (who may have access to for the Child Tax Credit) and other relatives you support. If you're unsure whether someone counts as your dependent, the IRS website has a dependent test tool.

You can also claim credits for child care expenses, education costs, or other situations. The form walks you through which credits apply. If you claim credits here, your withholding goes down — meaning less tax is taken from your paycheck.

Step 4: Account for multiple jobs or a working spouse

If you have more than one job, or if you're married and both spouses work, the IRS needs to know. The tax system assumes one income per person, so two jobs can push you into a higher tax bracket than either job alone would. This step helps prevent under-withholding.

If you have two jobs, you have two options: use the IRS Multiple Jobs Worksheet (included with the form) to calculate the right withholding for each job, or simply claim an extra amount of tax to be withheld from one paycheck each month. Many people choose the second option because it's simpler. If you're married and both work, you can use the worksheet or claim extra withholding on one spouse's W-4.

Step 5: Enter other income and deductions

If you have income that doesn't come with tax withholding — self-employment income, rental income, investment income, or unemployment benefits — you can account for it here. You can also claim deductions beyond the standard deduction if you itemize.

Most people leave this section blank. You only need it if you have significant non-wage income or if you itemize deductions on your tax return (rather than taking the standard deduction). If you're unsure, you can leave it blank and adjust later if needed.

Step 6: Sign and date, then give it to your employer

Sign and date the form at the bottom. Your employer must have a signed W-4 on file before they can withhold based on it. If you submit an unsigned form, they may not process it or may withhold using the default rate (which is usually higher).

Give the completed form to your employer's payroll or human resources department. Keep a copy for your records. Your employer will use it starting with your next paycheck, though some employers may wait until the following pay period.

When to file a new W-4

You don't need to file a new W-4 every year. File a new one only when your situation changes: you get married or divorced, you have a child, you take a second job, your income changes significantly, or you want to adjust how much tax is withheld.

If you got a large refund last year, that usually means you withheld too much. You can file a new W-4 and reduce your withholding. If you owed money, you withheld too little and should increase it. The IRS tax withholding calculator can help you figure out what to change.

Frequently Asked Questions

Can I claim zero dependents if I have children?

Yes. Claiming dependents on your W-4 reduces your withholding. If you want more tax withheld (for example, if you have other income or expect to owe), you can claim fewer dependents than you actually have, or claim zero. You'll still claim all your dependents on your tax return when you file.

What happens if I don't fill out a W-4?

Your employer must withhold tax from your paycheck. If you don't provide a W-4, they'll use the default withholding rate, which treats you as single with no dependents. This usually results in more tax being withheld than necessary. Submitting a W-4 lets you adjust that.

Do I need to file a new W-4 if I get a raise?

Not necessarily. A raise doesn't change your filing status or dependents, so your withholding should still be roughly correct. However, if your income changes dramatically, you can use the IRS calculator to check whether your withholding is still appropriate and file a new W-4 if needed.

What's the difference between the old W-4 and the new one?

The 2020 version removed the "allowances" system and replaced it with a simpler method based on filing status, dependents, and income. If you have an old W-4 from before 2020, your employer may ask you to file a new one. The new form is shorter and easier to understand.

Can I claim my spouse as a dependent on my W-4?

No. You can only claim dependents on your W-4 — people you support who are not your spouse. Your spouse's income and tax situation are handled separately through their own W-4 or through your joint tax return if you file jointly.