How to Fill Out a W-4 So Your Withholding Matches What You Owe

The redesigned Form W-4 doesn't ask for "allowances" anymore. Since 2020, it asks for your filing status and a handful of dollar amounts, and your employer feeds those directly into the IRS Publication 15-T Percentage Method to compute how much federal tax comes out of each paycheck. There's no lookup table of allowance numbers involved — it's the same bracket math used to calculate your annual tax, applied to your pay period.

Here's exactly what your employer calculates, worked with a real paycheck.

What your employer actually calculates

Publication 15-T's Worksheet 1 runs four steps on every paycheck:

1. Annualize your wages — multiply what you're paid this period by the number of pay periods in a year.
2. Apply the standard withholding adjustment — a stand-in for your standard deduction, subtracted from annualized wages unless you checked Step 2 on your W-4.
3. Run the result through the same percentage-method brackets used to calculate annual income tax, per Rev. Proc. 2024-61.
4. Subtract dependent credits, divide by pay periods, and add any extra withholding you requested.

Every dollar amount in this calculation comes from what you write on the W-4 itself.

Why the form changed in 2020

Before 2020, Form W-4 asked for a number of "allowances," each worth a fixed dollar amount subtracted from taxable wages. The 2017 Tax Cuts and Jobs Act eliminated the personal exemption that allowances were pegged to, so the IRS redesigned the form to ask for dollar amounts and filing status directly instead of an allowance count with no exemption left to size it against. That's why a pre-2020 W-4 on file with an old employer still uses allowance-based withholding tables, while every W-4 filed since uses the worksheet below.

Worked example: $3,000 biweekly, Step 2 unchecked

Take a single filer paid $3,000 every two weeks (26 pay periods a year) who leaves Steps 2 through 4 of the W-4 blank except Step 1 (filing status: single).

• Annualized wages: $3,000 × 26 = $78,000
• Standard withholding adjustment (Step 2 unchecked, single): subtract $15,000 — the 2025 single standard deduction
• Adjusted annual wage: $78,000 − $15,000 = $63,000
• Apply the 2025 single percentage-method brackets to $63,000:
  • 10% on the first $11,925 = $1,192.50
  • 12% on the next $36,550 (to $48,475) = $4,386.00
  • 22% on the remaining $14,525 (to $63,000) = $3,195.50
• Tentative annual withholding: $1,192.50 + $4,386.00 + $3,195.50 = $8,774.00
• Per-paycheck withholding: $8,774.00 ÷ 26 = $337.46

Over the year, that's $8,774 withheld against $78,000 of wages — an effective withholding rate of 11.25%, even though the last dollar of adjusted wage sits in the 22% bracket. The same marginal-vs-effective gap that shows up in your annual return shows up on every paycheck, for the same reason: only the wages inside each bracket get that bracket's rate.

Why checking Step 2 changes the number

Step 2 exists for people with more than one job, or a working spouse, at the same time. The standard withholding adjustment above assumes this paycheck is your only income and that your standard deduction should shelter part of it. If you actually have a second job, that assumption over-shelters you — each employer would independently apply the same $15,000 adjustment, so combined withholding across both jobs comes in too low.

Checking Step 2 removes the standard withholding adjustment entirely. Rerun the same filer with Step 2 checked and nothing else changed:

• Adjusted annual wage: $78,000 (no $15,000 subtracted)
• Tentative withholding: 10% × $11,925 + 12% × $36,550 + 22% × ($78,000 − $48,475) = $1,192.50 + $4,386.00 + $6,495.50 = $12,074.00
• Per-paycheck withholding: $12,074.00 ÷ 26 = $464.38

That's $126.92 more withheld per paycheck than the Step 2-unchecked version — the correction for the fact that, with two jobs, the standard deduction can't be claimed twice.

Steps 3 and 4: dependents, other income, and extra withholding

The rest of the form adjusts the same calculation directly:

• Step 3 (dependent credits) subtracts a flat dollar amount straight from tentative annual withholding, before dividing by pay periods.
• Step 4a (other income not subject to withholding) adds to annualized wages before the standard adjustment is applied — raising the base the brackets run against.
• Step 4b (deductions above the standard deduction) subtracts an extra amount from that same base.
• Step 4c (extra withholding) is the only step that isn't run through brackets at all — it's a flat dollar amount added to every paycheck's withholding, after everything else is calculated.

None of these change the mechanism — they change one of the inputs that the same Worksheet 1 arithmetic runs on.

Checking your own numbers before you submit the form

You can run your own pay frequency, filing status, and every W-4 step through the W-4 Withholding Estimator to see the exact per-paycheck withholding and effective rate this math produces — the same calculation worked above, for your actual paycheck, before you hand the form to your employer.