The household in the calculator
The page opens with a married couple filing jointly. One spouse earns $3,000 every two weeks, $78,000 a year; the other earns $60,000 at a second job. Each job’s W-4 lists only the filing status, so each employer withholds as if its paycheck were the couple’s whole income:
- The first job takes $78,000 − $12,900 = $65,100, which the 2026 married table withholds $5,000 on.
- The second takes $60,000 − $12,900 = $47,100: $2,840 for the year. That is what the calculator has under Other jobs and income.
Together that is $7,840. On the return, though, the couple’s $138,000 minus one $32,200 standard deduction leaves $105,800 of taxable income, and the 2026 brackets put about $12,700 of tax on it. The gap of roughly $4,860 is what they’d owe in April if nothing changed, with a possible underpayment penalty on top.
How the suggestion closes it
The calculator takes what has been withheld so far, adds both jobs’ remaining withholding, and spreads the gap over the paychecks left in 2026 as a Step 4(c) amount on the first job’s W-4. The Step 2 box stays unchecked, because the second job’s pay and withholding are already in the numbers. Early in the year the extra per paycheck is small; late in the year it is larger, because fewer paychecks are left to catch up.
Change the other job’s pay to your spouse’s, or to your own second job, and type its withholding so far plus what is still to come. A pay stub’s year-to-date figure plus its per-paycheck withholding times the paychecks left is the most accurate way to get it.
When the Step 2 box is the better tool
If both jobs pay about the same, checking the Step 2(c) box on both W-4s is simple and close: each employer then withholds with half the standard deduction and brackets half as wide. The calculator shows what that does if you tick the box under Your W-4 at this job now. With very different pay, or three jobs, use the Step 4(c) amount. In January, fill in new W-4s for 2027: the catch-up amount here is sized for this year’s remaining paychecks.