Form W-4 Step 4 is the block payroll uses when the regular percentage-method table is not enough: side income, deductions above the standard deduction, or a flat extra amount each payday. It does not compute FICA. It does not file your return.
On a $52,000 adjusted annual wage, single, biweekly, Step 2 unchecked, Publication 15-T already withholds $195.85 a check. Add $25 on Step 4(c) and that check becomes $220.85. Annual withholding becomes $5,742.10.
Open the W-4 Step 4 adjuster →
Step 4(a) and 4(b) follow Publication 15-T Worksheet 1A and the 2026 standard deduction in Rev. Proc. 2025-32 §2.14. Confirm the current Form W-4 instructions. This is not a refund guarantee.
The three Step 4 lines
| Line | What you enter | What payroll does | |---|---|---| | 4(a) Other income | Annual interest, dividends, 1099 side work you want withheld on this W-2 | Adds to the annual wage used in the percentage-method table | | 4(b) Deductions | Itemized or other deductions from the W-4 worksheet | Reduces annual wage only by the amount above the 2026 standard deduction | | 4(c) Extra withholding | Dollars per pay period, not per year | Adds a flat amount after the table |
deduction benefit = max(0, Step 4(b) − standard deduction for your status)
annual wage after Step 4 = max(0, base wage + 4(a) − deduction benefit)
period FIT = (Pub 15-T tentative on that annual wage) ÷ periods + Step 4(c)
2026 standard deductions in the calculator (Rev. Proc. 2025-32 §2.14):
- Single / married filing separately: $16,100
- Married filing jointly: $32,200
- Head of household: $24,150
If 4(b) is below that figure, the benefit is $0. Entering $10,000 of deductions on a single return does not cut withholding. The first $16,100 is already built into the Pub 15-T standard schedules.
Worked cases (same $40,000 base, single, 26 periods)
Start with $40,000 adjusted annual wage, single, Step 2 off. Tentative annual FIT is $1,240 + 12% × ($40,000 − $19,900) = $3,652.
| Step 4 inputs | Wage after Step 4 | Annual FIT |
|---|---|---|
| None | $40,000 | $3,652 |
| 4(a) +$5,000 other income | $45,000 | $4,252 |
| +$5,000 other and $20,000 deductions | $41,100 | $3,784 |
| $10,000 deductions only | $40,000 | $3,652 (no 4(b) benefit) |
The $20,000 itemized row: $20,000 − $16,100 = $3,900 benefit. $40,000 + $5,000 − $3,900 = $41,100. Tentative = $1,240 + 12% × $21,200 = $3,784.
Extra withholding is the simple lever
People who want a smaller refund gap often skip 4(a)/(b) and type a number on 4(c).
| Extra per biweekly check | FIT this check on $52,000 single | Annual FIT | |---|---|---| | $0 | $195.85 | $5,092.10 | | $25 | $220.85 | $5,742.10 | | $50 | $245.85 | $6,392.10 |
FICA on that $2,000 of wages stays $153.00 (6.2% + 1.45%) unless the wage boxes change. Step 4(c) is income-tax withholding only. Confirm on the paycheck calculator.
When Step 4 is the wrong tool
- Two W-2 jobs, no side income: start with Step 2, not a guess on 4(c). The federal withholding calculator shows the Step 2 schedule. Primer: federal tax withholding.
- Dependents / child-related credits: that is Step 3, a credit against tentative FIT, not a Step 4 deduction. The withholding tool models Step 3. This Step 4 page does not.
- Self-employment as the main income: there is no W-4 on a 1099. Use self-employment take-home and estimated tax safe harbor.
- A one-time bonus: many employers use the 22% supplemental rate instead of spreading the bonus across your W-4. See the bonus tax calculator.
Adding $5,000 on 4(a) only raises W-2 withholding. It does not compute self-employment tax on that $5,000. SECA is 12.4% + 2.9% on 92.35% of net earnings (Topic 554).
What this page is not
- Not the full W-4 PDF. Read the current form.
- Not a 50-state withholding form (some states have their own).
- Not Additional Medicare (0.9% after the statutory wage threshold). That is Additional Medicare tax.
No. It moves cash from each paycheck to the IRS during the year. The Form 1040 tax is computed later. Extra 4(c) can shrink a balance due or grow a refund. It does not change the 6.2% / 1.45% FICA rates.
On a single 2026 W-4, 4(b) only counts dollars above $16,100. $12,000 is still inside the standard deduction already baked into the Pub 15-T standard schedules.
You can ask this W-2 to withhold more. That is a cash-flow choice. It is not the same as computing SE tax or making quarterly estimates. If the gig is large, run the self-employment take-home numbers.
$195.85 is the table withholding on $52,000 single biweekly with Step 4 empty. Step 4(c) of $25 is what turns it into $220.85. The withholding calculator shows the table piece. This page adds 4(a)/(b)/(c).
About Form W-4 · Publication 15-T · Rev. Proc. 2025-32 §2.14 (standard deduction)