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A new hire hands you a 2026 Form W-4. Payroll has to turn it into one number: the federal income tax to withhold from each paycheck. IRS Publication 15-T calls the method Worksheet 1A, and for 2026 its tables changed.
Why the 2026 tables matter. Pub 15-T (2026) says its withholding tables were updated for P.L. 119-21, the One Big Beautiful Bill Act. The Single STANDARD table now starts at $7,500 of Adjusted Annual Wage Amount; the 2025 table started at $6,400. Take a Single employee paid $2,400 biweekly with nothing else on the W-4. On the 2026 table the withholding is $204.15 per paycheck. On last year's table it would be $209.60. That gap is small, but it shows that a payroll setup copied from 2025 is no longer the IRS method.
The box that moves the most money. Step 2 of the W-4 is for employees with two jobs or a working spouse. When the box is ticked, line 1g of Worksheet 1A becomes zero and you switch to the Step 2 Checkbox schedule, whose bands are half as wide. For the same $2,400 biweekly Single employee, the withholding jumps from $204.15 to $359.35. If payroll misses the tick, each paycheck is $155.20 short, which adds up to $4,035.20 over 26 paychecks. Section 3403 of the Internal Revenue Code is blunt: the employer is liable for the payment of the tax required to be withheld. Deposits that arrive late carry a 2%, 5% or 10% penalty under section 6656, depending on how many days late they are.
Filing status and Step 3. Married filing jointly uses a table that starts at $19,300, after a $12,900 line 1g amount. Head of household starts at $15,550. The same $2,400 biweekly paycheck gives $162.92 for Head of household. A married employee filing jointly who writes $4,400 in Step 3 has their credits divided by 26 and subtracted per paycheck; at $2,400 biweekly that brings the withholding to $0.00.
What the calculator does. You type eight entries: wages this pay period, pay frequency, filing status, the Step 2 checkbox, Step 3, Step 4(a), Step 4(b) and Step 4(c). It shows twelve Worksheet 1A lines, from 1c annual wages to 4b, the amount to withhold per paycheck. The bands come straight from the 2026 Annual Percentage Method tables. I checked the formulas against every row of all six IRS schedules: 35,472 test cases across weekly, biweekly, semimonthly and monthly pay, zero cents apart. The IRS rounds three thresholds of the Single Step 2 table to whole dollars, and the calculator keeps that rounding.
What it does not do. This is federal income tax only. Social Security, Medicare and state withholding are separate. It also does not replace the employee's W-4; it reads it.
Why not the IRS estimator. The Tax Withholding Estimator helps an employee plan their own refund. It does not show the employer's Worksheet 1A lines, and the employer is the one liable under section 3403.
The free check runs in the browser, with no account. If you want to keep a dated record per employee, the workbook holds the same twelve live formulas and the six official 2026 schedules.
15 seconds — what it actually does
Questions people ask
What does this W-4 calculator work out?
It runs IRS Publication 15-T (2026) Worksheet 1A for one employee: annual wages, Adjusted Annual Wage Amount, tentative withholding from the 2026 table for the filing status, Step 3 credits, Step 4(c) extra, and the federal income tax to withhold per paycheck. Example: Single, $2,400 biweekly gives $204.15; with the Step 2 box ticked, $359.35.
Who is it for?
Payroll staff, HR generalists, office managers and small-business owners who must set federal income tax withholding when an employee hands in a 2026 Form W-4. Employees can use it too, to see what their employer should withhold from each paycheck before they sign the form.
Why not use the IRS Tax Withholding Estimator?
The IRS estimator is built for employees planning their own refund. It does not show the employer's Worksheet 1A lines. An employer has to withhold what the Pub 15-T 2026 table says, and under IRC section 3403 the employer is liable for tax it was required to withhold and did not.
What is free?
The whole calculation is free in the browser: 8 W-4 inputs, 12 Worksheet 1A result lines, all 3 filing statuses, with or without the Step 2 checkbox, for every pay frequency from weekly to annual. Nothing is hidden or blurred, there is no account, and the answer is never locked.
What does the paid version add, and what does it cost?
For $21, paid once, you get the .xlsx workbook with the same 12 live formulas, recalculated in LibreOffice and matched to the web page. Save one copy per employee as the dated record of how 2026 withholding was set. Doing Worksheet 1A by hand takes a payroll clerk's time; BLS OEWS 2025 puts their median at $28.01 an hour.
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