01The layers between gross and net
Federal income-tax withholding is progressive and follows your Form W-4. FICA is separate: employees pay 6.2% for Social Security up to the $184,500 wage base and 1.45% for Medicare. Employers begin withholding the additional 0.9% Medicare tax when an employee’s wages pass $200,000, regardless of filing status.
Traditional 401(k) deferrals reduce income-tax wages but remain subject to FICA. Eligible payroll HSA and Section 125 benefits generally reduce both. Roth 401(k) contributions and other post-tax deductions reduce the cash you receive without reducing current taxable wages.
Worked anchor: a single filer with $75,000 of wages, no deductions and no state tax has $7,670 of federal tax and $5,737.50 of FICA in 2026, leaving $61,592.50 before any state, local or voluntary deductions.
02What the 2026 W-4 changes
Swiftly uses IRS Publication 15-T Worksheet 1A. It annualizes taxable wages, applies Step 4(a) other income and Step 4(b) deductions, uses the Step 2 checkbox schedule when selected, subtracts Step 3 credits, and adds Step 4(c) extra withholding to each paycheck.
The withholding check compares that payroll estimate with a one-job annual tax projection. Step 2 is different: because the missing spouse or other-job income was not entered, the tool does not invent a household refund or balance-due prediction.
- Step 2 covers multiple jobs or a working spouse and generally increases withholding.
- Step 3 is a dollar tax credit; it is not another income deduction.
- Step 4(c) is extra dollars per paycheck, not an annual amount.
- A separately paid bonus may use 22% flat supplemental withholding, or 37% above $1 million; aggregate withholding is also possible.
03Pre-tax versus Roth and after-tax deductions
Traditional 401(k) contributions reduce current income-tax wages. The 2026 employee deferral limit is $24,500, with an $8,000 catch-up at age 50 and an $11,250 catch-up from age 60 through 63. Roth contributions are after-tax and belong in the post-tax deduction field.
The 2026 HSA limit is $4,400 for self-only HDHP coverage and $8,750 for family coverage, plus $1,000 at age 55 or older. Employer contributions count toward the same limit. Payroll HSA contributions can reduce FICA; a direct contribution outside payroll does not follow the same paycheck treatment.
04Pay frequency and cash-flow planning
A $78,000 salary is $1,500 weekly, $3,000 bi-weekly, $3,250 semi-monthly or $6,500 monthly before taxes and deductions. Bi-weekly means 26 checks; semi-monthly means 24. The annual total is the same, but the cash arriving in a given month is not.
Budget on annualized net divided by 12 rather than multiplying a bi-weekly check by two. This calculator spreads a recurring annual estimate evenly. A specific pay stub can differ because of year-to-date wage caps, benefit timing, exact state or local rules and payroll rounding.