Skip the math — get your exact Step 4 numbers in 60 seconds.
Open the free calculator →TL;DR
- 4a — other income not from a job (interest, dividends, retirement): increases withholding
- 4b — Deductions Worksheet total (itemizing, tips, overtime, seniors, more): decreases withholding
- 4c — flat extra amount per paycheck: the most flexible tool on the form
- All three are optional — leave blank if your situation is straightforward
Step 4a — Other income (annual)
Enter the annual total of income you receive that isn't subject to withholding — income where no employer is automatically taking out taxes on your behalf.
Entering income in 4a doesn't pay the tax directly — it tells your employer to withhold more to cover the income tax on that amount. The 2026 Form W-4 says not to include income from any job or from self-employment in 4a. For freelance income, use the IRS estimator or put the tax in Step 4c. See the guide on W-4 for freelance and 1099 income.
Step 4b — Extra deductions (annual)
Most people take the standard deduction — $16,100 for single filers and $32,200 for married filing jointly in 2026. If you don't, and you itemize on Schedule A, Step 4b lets you reduce your withholding to account for those deductions.
Important: Step 4b takes the total from the Deductions Worksheet on the W-4 (line 15). For itemizers that is the amount by which your itemized deductions exceed the standard deduction, not your total itemized deductions. Even if you take the standard deduction, the worksheet also has lines for qualified tips, overtime, passenger vehicle loan interest, seniors 65+, student loan interest and IRA contributions (see the 2025 tax law and your W-4).
📊 Step 4b example — homeowner who itemizes
Mortgage interest: $18,000
Property taxes + state income tax (SALT): $14,000
Charitable donations: $3,000
Total itemized: $35,000
Single standard deduction: $16,100
Step 4b entry: $35,000 − $16,100 = $18,900
With the SALT cap raised from $10,000 to $40,400 for 2026 under OBBBA, more homeowners in high-tax states can now benefit from itemizing. See buying a home and your W-4 for details.
Step 4c — Extra withholding per paycheck
Step 4c is the most flexible line on the W-4. Enter a flat dollar amount and your employer adds it to every paycheck's withholding — no questions asked, no explanation required.
Not sure what number to write? The formula and worked examples are in our Step 4(c) guide, and how to stop owing taxes shows how to find the shortfall first.
It's the right tool when you know you need more withholding but want to control the amount precisely — rather than letting the IRS tables determine it.
Cover a gap from the IRS estimator
If the estimator says you'll owe $780 and you have 13 paychecks left, enter $60 in Step 4c.
Cover tax on side income
The IRS says to use its estimator for self-employment income. By hand: self-employment tax is net profit × 0.9235 × 0.153, plus income tax on the profit; divide the total by your pay periods and enter it in Step 4c.
Safety buffer
Even $25–$50/paycheck over a full year can prevent a surprise April bill.
Fine-tune after using 4a or 4b
If 4a and 4b don't quite get you where you want, 4c is the precision adjustment.
Calculate your Step 4 amounts — free
Enter your other income and deductions to get the exact amounts for Steps 4a, 4b, and 4c.
Open the W-4 Calculator →What's on page 4 of the W-4?
Page 4 of the 2026 W-4 is the Deductions Worksheet. Its line 15 total is what you enter in Step 4(b). If you want lesstax withheld, this is the lever: list your itemized deductions above the standard deduction and any of the new tips, overtime, car loan or senior deductions, and a bigger Step 4(b) lowers each paycheck's withholding. If you want more withheld, use Step 4(c) instead.
When to leave all of Step 4 blank
If you have a single W-2 job, take the standard deduction, and have no non-wage income, you can leave Steps 4a, 4b, and 4c entirely blank. The IRS withholding tables will produce a reasonable result for your filing status, and you'll likely get a small refund or owe a small amount — both within normal range.
Key terms in this article
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