2026 Form W-4 field guide

W-4 Step 4(a) and 4(b): Other Income and Deductions

Who completes it

Workers with taxable interest, dividends, retirement income, or deductions not already reflected in payroll withholding.

Use annual amounts, not per-paycheck amounts. Do not include job wages in Step 4(a), and use the deductions worksheet before entering Step 4(b).

A worker expecting $6,000 of taxable interest can put $6,000 on Step 4(a), allowing payroll tables to withhold as if annual income were higher.

Entering a per-paycheck amount instead of an annual amount
Adding self-employment revenue without accounting for separate self-employment tax
Claiming the full itemized deduction rather than only the worksheet adjustment

Will my employer see the source of Step 4(a) income?

No. Form W-4 asks for an amount, not the source. The IRS estimator can instead translate the effect into extra withholding on Step 4(c).

Can I leave Step 4(a) blank and use Step 4(c)?

Yes. Extra withholding can be used when you prefer not to disclose other income or when a fixed per-paycheck adjustment is easier to manage.