How the W-4 Works

Why the W-4 changed

Before 2020, employees claimed a number of "allowances" — a rough proxy for dependents and deductions that reduced taxable wages by a fixed amount per allowance. The 2017 tax law changes (which removed personal exemptions and roughly doubled the standard deduction) made that system a poor fit, so the IRS redesigned the form to work in direct dollar amounts instead. If your W-4 on file predates 2020 and you haven't updated it, your employer can still use it — old-style allowances are still supported behind the scenes — but any new form you fill out today uses the redesigned four-step version.

Step 1: Filing status

Single, Married Filing Jointly, or Head of Household. This alone changes which rate schedule your withholding is calculated against — the same wages produce different withholding depending on this single choice, because each status has its own set of tax brackets.

Step 2: Multiple jobs or a working spouse

This is the step most people get wrong. If you hold more than one job at once, or you're married filing jointly and your spouse also works, checking this box tells your employer to withhold at a higher rate — because the standard withholding tables otherwise assume this is your only source of income for the year, and would under-withhold if you actually have two incomes stacking into higher brackets.

Concretely: leaving Step 2 unchecked applies a standard deduction-like allowance built into the withholding formula ($8,600 for most filers, $12,900 for married filing jointly in 2026) before tax is calculated. Checking the box removes that allowance and applies a steeper rate schedule instead — both mechanisms exist in the same official worksheet (IRS Publication 15-T, Worksheet 1A) that employers use to calculate withholding either way.

Step 3: Dependents and other credits

Enter a dollar amount here — not a count of dependents — representing tax credits you expect to claim (commonly the Child Tax Credit and Credit for Other Dependents). Your employer divides this annual amount evenly across your pay periods and subtracts it directly from your withholding, dollar for dollar. This step lowers withholding; it doesn't touch your taxable wages.

Step 4: Other adjustments (optional)

Three separate, independent entries:

• 4(a) — Other income. Income not from jobs (interest, dividends, retirement income) that you want withholding to account for, so you don't owe a lump sum at filing.
• 4(b) — Deductions. Itemized or other deductions beyond the standard deduction, reducing the wages withholding is calculated on.
• 4(c) — Extra withholding. A flat additional dollar amount withheld every pay period, on top of everything else — useful for covering self-employment income, multiple-job gaps Step 2 doesn't fully capture, or simply wanting a bigger refund.

Why two people with the same salary can take home different amounts

Every one of these four steps changes the withholding calculation independently. Two coworkers earning the exact same salary can have meaningfully different paychecks if one is married filing jointly with a working spouse (Step 2 checked) and claims two dependents (Step 3), while the other is single with no Step 2 or 3 entries. Withholding is an estimate toward what you'll actually owe — it isn't your final tax bill — but the W-4 is the main lever you control over how close that estimate lands to zero at filing.

See it computed for your own numbers

The paycheck calculator includes all four W-4 steps and shows exactly how each one changes your withholding, line by line.