The Percentage Method: How Employers Calculate Withholding
Most payroll systems use the percentage method: (1) Start with gross wages for the pay period. (2) Add Step 4a income (from W-4). (3) Subtract Step 4b deductions (from W-4). (4) Subtract the "Adjusted Amount for Withholding" based on filing status and pay frequency (replaces the old personal allowance reduction). (5) Apply the withholding tax table to the resulting amount. (6) Add Step 4c extra withholding. (7) Subtract Step 3 credits divided by pay periods. Result = withholding for this paycheck.
IRS percentage method withholding calculation — $75,000 salary, biweekly, single filer
| Calculation Step | For Biweekly Pay, Single, $75,000/yr | Impact |
|---|---|---|
| Gross wages per period | $2,885 | Starting point |
| Add Step 4a income (if any) | $0 | Increases amount subject to withholding |
| Subtract Step 4b deductions | $0 | Decreases amount subject to withholding |
| Subtract adjusted amount | ($448) | Accounts for standard deduction portion per period |
| Taxable wage for withholding | $2,437 | Amount the withholding table is applied to |
| Apply tax table percentage | 22% of amount in bracket | ~$480 |
| Add Step 4c extra | $0 | User-specified extra |
| Subtract Step 3 credits per period | $0 | Reduces withholding for dependents |
| Total withholding | ~$480/biweekly | Federal income tax withheld this paycheck |
How Each W-4 Line Affects the Formula
Step 4a (Other Income): added to gross wages — every dollar entered increases taxable wage and withholding. Step 4b (Deductions): subtracted from gross wages — reduces taxable wage and withholding proportionally. Step 4c (Extra withholding): added directly to final withholding — a flat additional amount regardless of wages. Step 3 (Credits): divided by pay periods and subtracted from final withholding — directly reduces withholding per period.
If your wages are uneven throughout the year (overtime, bonuses, raises), your withholding may increase in December to ensure year-to-date withholding matches your full-year liability. The annualized method payroll systems use can cause this 'catch-up' effect in higher-income months.
Calculate Your Exact Withholding Per Paycheck
Enter your salary, filing status, and W-4 settings to see the precise per-paycheck withholding the IRS formula produces.