Single-employee payroll tax calculator — before and after an additional $1,220 monthly pre-tax deduction. This is an estimate only. SIMERP healthcare benefits work alongside existing benefits. Does not run payroll, file taxes, or replace advice from your payroll provider, CPA, attorney, or compliance team.

→ Upload a payroll census for a full group comparison

Tax year 2026. Withholding is computed on 95% of gross base pay as a conservative buffer. Federal withholding uses IRS Publication 15-T percentage-method tables; every wage-withholding state and DC uses its official 2026 withholding method. Reciprocity certificates, nonresident apportionment, and local or municipal taxes (e.g. NYC, PA locals, MD county tax) are out of scope.

Single employee

Pre-tax deductions (this pay period)
Federal W-4 details (optional)

Leave these blank/defaulted to use the standard no-adjustment estimate. Enter employee-specific Form W-4 details when they are available from the payroll record.

Before and after comparison

Enter employee details and select Calculate comparison to see an estimated before and after breakdown.

Payroll census upload monthly output

Paste a payroll census export to generate one spreadsheet-style output with before, after, Monthly Gross Tax Reduction, Monthly Fee, and Monthly Net Tax Reduction columns. Every calculated result is normalized to monthly numbers regardless of the input pay frequency.

Each provider exports columns differently. The normalizer will map them to the fields this estimate needs: employee reference, gross wages, pay frequency, YTD Social Security wages, YTD Medicare wages, health (Section 125), traditional 401(k), other pre-tax deductions, and work state, plus optional federal W-4 fields when available.

Try a quick CSV calculation

Paste comma-separated rows with a header line. The output table and download use monthly before, after, Monthly Gross Tax Reduction, Monthly Fee, and Monthly Net Tax Reduction columns. The added $1,220 pre-tax deduction is treated as monthly and prorated into each input pay period before calculating the monthly comparison. Optional federal W-4 columns: federalFilingStatus, federalStep2Checkbox, federalStep3Credits, federalStep4aOtherIncome, federalStep4bDeductions, federalStep4cExtraWithholding, and federalExempt.

EE fee defaults to $149. If the plan has an employer cost (e.g. total $189, EE $149, employer $40), enter the total fee to calculate the employer FICA reduction.