W-4 Step 4 Withholding Adjuster 2026
Most employees fill Steps 1 and 2 of Form W-4 and stop. Step 4 is where you fix a paycheck that's either starving or drowning you: it tells your employer to tax income you earn elsewhere, to honor big itemized deductions, or to withhold a flat extra amount every period. This calculator shows what each lever does using the official 2026 Pub 15-T percentage-method tables.
annual wage = (Steps 1/2 wage) + 4(a) other income − 4(b) deduction benefit
4(b) benefit = max(0, deductions − 2026 standard deduction)
tentative annual = percentage-method table for your status
per period = tentative ÷ periods + 4(c) extra
The three levers
| Step | What you enter | Effect | |---|---|---| | 4(a) other income | Interest, dividends, freelance, side gigs | Raises withholding — that income otherwise arrives untaxed | | 4(b) deductions | Itemized/other deductions (full amount) | Lowers withholding — but only the part above the $16,100 / $32,200 / $24,150 standard deduction (single / MFJ / HoH) | | 4(c) extra per period | Flat dollar amount | Adds that amount to every paycheck, the most direct anti-balance-due lever |
The standard-deduction netting is done for you: the paper W-4 asks for a pre-netted number, which is the single most common Step 4(b) mistake. Here you enter the full figure.
Worked example
Single, Steps 1/2 wage $40,000, biweekly, no Step 2:
- Base: $40,000 → $1,240 + 12% × ($40,000 − $19,900) = $3,652/yr → $140.46 per period
- Add 4(a) $5,000 of freelance income → $45,000 → $4,252/yr → $163.54 (+$23.08 per paycheck)
- Add 4(b) $20,000 itemized deductions → benefit $3,900 → back down to $41,100 → $3,784/yr → $145.54
- Add 4(c) $25 extra per period → $170.54 per period, $4,434/yr
The dependents credit (Step 3) applies after the tentative amount with its own phase-out bands tied to adjusted gross income, so it is out of scope for this first-look tool. For the full calculation use the IRS Tax Withholding Estimator. Educational estimate from IRS Pub 15-T (Rev. Dec. 2025) and Rev. Proc. 2025-32 §2.14; not tax advice.
Official sources
- IRS Publication 15-T (2026) — percentage method tables
- Form W-4 (2025) — the form itself, Steps 1–4
- Rev. Proc. 2025-32 — 2026 standard deduction (§2.14)
Related tools (United States):
The optional adjustments that fine-tune withholding: 4(a) other annual income with no withholding of its own, 4(b) itemized deductions that only help above the standard deduction, and 4(c) a flat extra dollar amount withheld every period.
The paper W-4 asks for the net value, but in this calculator enter the full amount: it nets against the 2026 standard deduction for your filing status automatically (Rev. Proc. 2025-32: $16,100 single, $32,200 married joint, $24,150 head of household).
The dependents credit applies after the tentative amount with its own phase-out bands tied to adjusted gross income, which is out of scope for this first-look estimate. Use the IRS Tax Withholding Estimator for the full calculation.