The W-4 form sits between you and your paycheck — and most people fill it out once when they start a job and never think about it again. Here’s what it actually does and why it matters.
What a W-4 does
A W-4 (Employee’s Withholding Certificate) tells your employer how much federal income tax to withhold from each paycheck. The amount withheld goes to the IRS throughout the year as advance payment of your annual tax bill. If too much is withheld, you get a refund in April. If too little, you owe money — sometimes with penalties.
The new W-4 format (post-2020)
The IRS redesigned the W-4 in 2020. The old system used “allowances” — the new one uses actual dollar amounts, which is more accurate but requires a bit more thought. Steps on the form:
- Step 1: Personal info and filing status (single, married, head of household)
- Step 2: Multiple jobs or a working spouse — critical if applicable
- Step 3: Claim dependents — reduces withholding
- Step 4: Other adjustments (other income, deductions, extra withholding)
- Step 5: Sign and date
The most common mistakes
Not updating Step 2 when you have multiple jobs or a working spouse. This is the #1 cause of owing money at tax time. If both spouses work and neither adjusts for the combined income, both will under-withhold. The IRS withholding estimator (irs.gov/W4App) calculates the right amount precisely.
Big refund vs owing money
A large tax refund isn’t “winning” — it means you gave the government an interest-free loan all year. Ideally, you want to owe nothing and receive nothing — or owe a small amount (under $1,000). If you consistently get large refunds, adjust your W-4 to withhold less. You’ll see more money in each paycheck throughout the year.
When to update your W-4
Revisit your W-4 whenever: you get married or divorced, you have a child, you start a second job, your spouse starts or stops working, you buy a home (mortgage interest deduction), or you have a major income change. Life changes affect your tax situation, and your withholding should reflect your current reality.