W-4 Withholding Calculator

Each employer withholds as if its paycheck is the household's only income. With two paychecks both doing that, your combined withholding under-shoots the joint tax bill, often by $1,000–$3,000.

Checking the Step 2(c) box on both W-4s tells each employer to use the higher withholding tables that assume a second income. That alone fixes most of the gap.

The W-4 form was rebuilt in 2020 to remove the old "allowances" system. Now each employer projects your taxes as if its paycheck is your only household income. That's fine for single-earner families. For everyone else (married couples where both work, anyone with a side W-2 job, anyone with bonus or commission income) the math breaks.

The fix is two-part. Check the Step 2(c) box on every W-4 in your household, then use Step 4(c) to add the residual shortfall as a flat dollar amount per paycheck. The number above tells you exactly what to enter. For deeper tax planning across the year, J.K. Lasser's Your Income Tax 2026 walks through every line of the W-4 and the 1040 in plain English.