The W-4 tells your employer how much tax to withhold from each paycheck

The W-4 is a form you fill out for your employer that controls how much federal income tax comes out of your paycheck. You do not send it to the IRS — you give it to your employer's payroll department. The information on it determines your withholding, which is the amount your employer sets aside from your pay and sends to the government on your behalf.

Without a W-4, your employer would withhold based on a default rate that usually results in too much tax taken out. By filling one out, you can adjust the withholding to match your actual tax situation — which means you might get more money in each paycheck instead of waiting for a refund at tax time.

You fill out a W-4 when you start a new job, and you can fill out a new one whenever your life changes in a way that affects how much tax you owe. The form itself is free and takes about 10 minutes if you have basic information about your income and dependents.

Key Takeaways

  • The W-4 is a form you give to your employer, not the IRS, and it controls how much federal income tax is withheld from your paycheck.
  • The amount you withhold depends on your filing status, number of dependents, other income, and whether you have a second job or spouse who works.
  • You can change your W-4 at any time during the year if your situation changes, such as getting married, having a child, or taking a second job.
  • If too much tax is withheld, you get a refund when you file your tax return; if too little is withheld, you owe money.

What information goes on a W-4

The current W-4 form (redesigned in 2020) asks for your name, address, and Social Security number so your employer can match the form to your payroll record. It also asks for your filing status — single, married filing jointly, married filing separately, or head of household — because each status has different tax brackets and withholding rates.

The form then asks about dependents. A dependent is usually a child or other family member you claim on your tax return, and each dependent reduces the amount of tax withheld. You enter the number of dependents you expect to claim when you file your tax return that year.

If you have income beyond your job — such as interest, dividends, rental income, or self-employment income — you report that on the W-4 as well. The same applies if your spouse works and you file jointly. These additional income sources increase your total tax liability, so the form accounts for them by increasing your withholding.

How the W-4 changes your withholding amount

Your employer uses the information on your W-4 to calculate a withholding amount based on IRS tables. The more dependents you claim, the less is withheld. The more other income you report, the more is withheld. Your filing status also affects the calculation because single filers and married filers have different tax rates.

If you want to adjust your withholding beyond what the form calculates, you can use the "Other income" or "Deductions" sections to fine-tune it. For example, if you know you will owe a lot of tax because of self-employment income, you can enter an extra amount to be withheld each pay period. If you want less withheld, you can reduce the number of dependents you claim (though this does not change your actual tax liability — it only changes what comes out now versus what you owe later).

The IRS provides a W-4 calculator on its website that walks you through the form step by step and suggests withholding amounts based on your situation. Using the calculator takes longer than guessing, but it usually results in withholding that is closer to what you actually owe.

When you need to fill out a new W-4

You must fill out a W-4 when you start a new job. Your employer will ask for it during onboarding, usually along with an I-9 form (which verifies you are authorized to work) and a W-9 or state tax form.

You can also fill out a new W-4 at any other time if your situation changes. Common reasons include getting married or divorced, having a child, taking a second job, your spouse starting or stopping work, or a significant change in your income. You do not have to wait for a specific date — you can submit a new W-4 whenever you want, and it takes effect on your next paycheck.

If you do not update your W-4 when your situation changes, your withholding may no longer match your tax liability. For example, if you get married and do not update your form, you might have too much withheld because you are still using single-filer withholding. If you have a child and do not update, you might have too little withheld because you are not accounting for the child tax credit.

What happens if your withholding is wrong

If your employer withholds too much tax during the year, you will receive a refund when you file your tax return. The IRS does not pay interest on refunds, so the money you overpaid sits with the government until you file and claim it back. Some people prefer this because it forces them to save; others prefer to adjust their W-4 so they take home more money each month.

If your employer withholds too little tax, you will owe money when you file your return. You have to pay the balance by the tax important date (usually April 15). If you owe a large amount, you may also owe a penalty for underpayment, though the IRS waives this penalty in some situations, such as if you had no tax liability the previous year.

The goal of filling out a W-4 correctly is to get your withholding as close as possible to what you actually owe, so you do not have a large refund or a large bill at tax time. This is not always possible — life changes mid-year, income fluctuates, and tax law changes — but starting with an accurate W-4 puts you in a better position.

W-4 and other tax forms

The W-4 controls federal income tax withholding only. If your state has an income tax, you will also fill out a state withholding form, which works the same way. Some states use a form similar to the federal W-4; others use a different format. Your employer will provide the state form when you start.

The W-4 is different from a W-2, which you receive after the year ends. A W-2 reports how much you earned and how much tax was withheld during the year. You use the W-2 to file your tax return. The W-4 is what you fill out to control the withholding that appears on the W-2.

If you are self-employed or have income that is not subject to withholding, you do not fill out a W-4 for that income. Instead, you pay estimated taxes directly to the IRS four times a year using Form 1040-ES.

Frequently Asked Questions

Can I claim zero dependents on my W-4 to have more tax withheld?

Yes. Claiming fewer dependents than you actually have will increase your withholding. This is a common way to adjust your withholding if you have other income or expect to owe tax. However, when you file your return, you claim the correct number of dependents, so you will get a refund for the extra withholding.

What happens if I do not fill out a W-4?

Your employer cannot pay you without a W-4. You must complete one before your first paycheck. If you do not submit one, payroll will follow up with you. If you still do not submit one, your employer may use a default withholding rate, which is usually the highest rate and results in a lot of tax being withheld.

Do I need to update my W-4 every year?

No. Your W-4 stays in effect until you change it. However, the IRS recommends reviewing it each year, especially if your life or income changed. You can also use the IRS calculator annually to see if your withholding is still accurate.

Can my employer refuse to process a new W-4?

No. Your employer must process a new W-4 when you submit it. The new withholding takes effect on your next paycheck. However, some employers have payroll processing schedules, so there may be a short delay between when you submit the form and when the new withholding starts.

What if I am married and both my spouse and I work?

You should both fill out W-4s that account for the fact that you have two incomes. The IRS calculator asks about this and will suggest withholding amounts for each of you. If you do not account for both incomes, you may have too little withheld and owe tax at the end of the year.