How to Fill Out a W-4 Form: A Step-by-Step Walkthrough

What a W-4 Does and Why You Fill One Out

A W-4 is the form you give your employer to tell them how much federal income tax to take from each paycheck. Your employer sends that money to the IRS on your behalf. If you get the W-4 wrong, you'll either have too much taken (and get a refund later) or too little taken (and owe money when you file taxes). The form itself is short, but the decisions on it matter to your actual take-home pay.

You fill out a W-4 when you start a new job, and you can change it anytime your life changes — if you get married, have a child, take a second job, or your spouse starts working. The IRS updated the W-4 in 2020, so if you haven't filled one out since before then, the new version looks different from what you remember.

Key Takeaways

• The W-4 has five steps: your name and address, your filing status, your jobs and income, your dependents, and any extra tax you want withheld.
• Your filing status (single, married, head of household) is the biggest factor in how much tax comes out — married couples filing jointly usually have less withheld than two single people earning the same total.
• If you have a spouse who also works, or if you have a second job yourself, you need to tell your employer on Step 2(c) so the withholding is correct.
• You can claim dependents (children under 17, or other relatives you support) on Step 3, which lowers the tax withheld from your pay.
• If you want extra money withheld each paycheck — to avoid owing taxes later — you enter that amount on Step 4(c).

Step 1: Fill in Your Personal Information

At the top of the form, write your full name, home address, and Social Security number exactly as they appear on your Social Security card. Your employer uses this to match the W-4 to your payroll records. If your name or address changes later, you can file a new W-4 — you don't have to wait for anything.

Check the box for your filing status. This is how you will file your taxes: single, married filing jointly, married filing separately, or head of household. If you're not sure which one applies to you, the IRS website has a tool to help you figure it out. Your filing status is the single biggest factor in how much tax your employer withholds, so getting this right matters.

Step 2: Claim Your Job and Tell Your Employer About Other Income

In Step 2(a), enter the job title or employer name — this is just for your records so you know which W-4 is which if you work multiple jobs. Step 2(b) asks if you want to use the "standard deduction" method or the "tax tables" method. Most people leave this blank and use the standard method, which is simpler.

Step 2(c) is critical if your situation is not straightforward. Check this box if any of these are true: you have a spouse who also works, you have more than one job, or your spouse has more than one job. When you check this box, your employer knows to withhold more tax because your household income is higher than just your single job. If you don't check it and you should have, you'll owe money at tax time.

Step 3: Claim Your Dependents

A dependent is someone you support financially and who lives with you for most of the year. For most people, this means children under age 17. You can also claim other relatives — a parent, a sibling, a grandchild — if you provide more than half their financial support and they live with you. Each dependent you claim lowers the amount of tax withheld from your paycheck.

On line 3(a), enter the number of children under 17 you claim. On line 3(b), enter the number of other dependents. If you're not sure whether someone counts as your dependent, the IRS has a worksheet on their website to help you decide. Don't guess — if you claim someone you shouldn't, you may have to pay back the tax savings plus penalties.

Step 4: Adjust Your Withholding if You Want To

Step 4 is optional and is for people whose situation is more complex. Step 4(a) and 4(b) are worksheets to calculate whether you need to adjust your withholding — most people skip these. Step 4(c) is where you can ask your employer to take out extra tax from each paycheck if you want to. Some people do this to avoid owing money when they file taxes, or to get a bigger refund.

If you have income that your employer doesn't know about — side work, rental income, investment income — you can enter an extra amount here to cover the tax on that income. For example, if you freelance on weekends and make $5,000 a year, you might ask your employer to withhold an extra $50 per paycheck to cover the tax on that side income. This is optional, but it can save you from a surprise tax bill.

Step 5: Sign and Date the Form

At the bottom, sign and date the form. You must sign it — an unsigned W-4 is not valid. Write today's date. Then give the form to your employer's payroll or human resources department. Keep a copy for your records.

Your employer should start using the new withholding on your next paycheck. If you don't see a change within two pay periods, ask your payroll department to confirm they received and processed the form.

When to File a New W-4

You don't have to file a new W-4 every year. You only need to file a new one when something changes. Common reasons include: you get married or divorced, you have a child, you take a second job, your spouse starts or stops working, you claim a dependent who moves out, or you realize you're having too much or too little withheld.

If you had a big refund last year, that means too much was withheld — you can file a new W-4 to lower the withholding. If you owed money, too little was withheld — file a new W-4 to raise it. You can file a new W-4 anytime, and the change takes effect on your next paycheck.

Frequently Asked Questions

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

Your employer is required to withhold taxes from your pay. If you don't give them a W-4, they will use a default withholding, which is usually higher than necessary. You should fill one out so your withholding matches your actual situation.

Can I claim zero dependents even if I have children?

Yes, you can claim fewer dependents than you actually have, which means more tax will be withheld. Some people do this to get a bigger refund. However, you cannot claim more dependents than you actually have — that is tax fraud.

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

No. A raise does not change your filing status or number of dependents, so your withholding stays the same. However, if the raise pushes you into a higher tax bracket and you want to adjust your withholding, you can file a new W-4.

What if my spouse and I both work and we're not sure about Step 2(c)?

Check the box. When both spouses work, the combined income can push you into a higher tax bracket, and your employer needs to know that to withhold the right amount. If you're unsure, it's safer to check the box than to leave it blank.

Can I change my W-4 in the middle of the year?

Yes. You can file a new W-4 anytime. The new withholding takes effect on your next paycheck. This is useful if you have a major life change — a new child, a spouse starting work, or a second job — partway through the year.