W-4 Form: Tax Withholding Tips to Optimize Your Taxes This Year

What is a W-4? What does it tell your employer? Knowing how this IRS form works can help with new jobs, tax refunds, and avoiding estimated tax payments.

image of the IRS W-4 form with a pen on it
(Image credit: Getty Images)

When you start a new job, your employer will ask you to complete a W-4 form. The IRS W-4 helps determine the correct amount of income tax your employer will withhold from your wages.

But how does it do that? And where do you go if you want to update your W-4? 

We'll cover what this important tax document is, and then list ten key items stressing the importance of correctly filling out and updating the W-4 form. After that, we’ll briefly mention common mistakes with the W-4 as well as how state withholding forms may differ from federal.

What is a W-4? 

The IRS Form W-4, Employee's Withholding Certificate, is a tax document you fill out so your employer knows how much tax to withhold from every paycheck.* Information like expected filing status, family income from other jobs, and number of dependents are used to calculate how much taxes must be withheld from your payment and remitted to the applicable tax agency.

*Note: Self-employed individuals and those with other tax situations may also use the W-4 form to calculate withholding; more on that below.  

Rocky Mengle

Rocky Mengle was a Senior Tax Editor for Kiplinger from October 2018 to January 2023 with more than 20 years of experience covering federal and state tax developments. Before coming to Kiplinger, Rocky worked for Wolters Kluwer Tax & Accounting, and Kleinrock Publishing, where he provided breaking news and guidance for CPAs, tax attorneys, and other tax professionals. He has also been quoted as an expert by USA Today, Forbes, U.S. News & World Report, Reuters, Accounting Today, and other media outlets. Rocky holds a law degree from the University of Connecticut and a B.A. in History from Salisbury University.

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