W-4 Step 4(c): Extra Withholding Per Paycheck

How Step 4(c) works

Step 4(c) is a flat dollar amount added to the federal income tax payroll has already calculated for the period. It does not interact with brackets, filing status, or the other steps: payroll runs its normal computation and then adds the figure you wrote. That is what makes it the simplest line on the form and the easiest one to size wrongly.

The line has two ordinary uses. The first is carrying a worksheet result: the Multiple Jobs Worksheet divides its annual figure by the number of pay periods per year at the highest-paying job and instructs you to enter the result in Step 4(c) on that job’s Form W-4, plus any other additional amount you want withheld. The second is closing a shortfall you projected yourself, or covering income you would rather not describe on Step 4(a).

Timing behaves differently here than with estimated tax. Publication 505 explains that federal income tax withheld is treated as paid evenly throughout the year regardless of when it was actually withheld. An amount added on Step 4(c) in the autumn is therefore credited across the whole year, which is why Step 4(c) can repair an underpayment that a fourth-quarter estimated payment would only partly cure.

Size the entry against a safe harbor rather than against the exact bill. Publication 505 sets the general thresholds at 90% of the current year’s tax, or 100% of the prior year’s tax and 110% where prior-year adjusted gross income was over $150,000, with no penalty where the balance owed comes to less than $1,000.

Divide by the paychecks that will actually carry the change. Publication 505 says the employer must put a new Form W-4 into effect no later than the start of the first payroll period ending on or after the 30th day after you submit it, so a form handed in late in a month may miss the next one or two pay dates. Confirm the figure on the first pay statement that shows it rather than assuming it took effect.

Step 4(c) only adds. To reduce withholding that is running too high, rework Steps 2 through 4(b) or return to the estimator; there is no negative entry on the printed line. A temporary amount also needs removing: an entry made to fix one year keeps withholding at the higher rate until a new Form W-4 replaces it.