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Privacy-first paycheck audit

Check your paystub line by line

Enter totals from one paycheck—no name, employer, or account details. Check whether the lines add up, then compare federal withholding and FICA using your W-4 and year-to-date wages. Nothing is uploaded or saved.

1. Paycheck context

Use the same pay period and filing assumptions shown in your payroll profile. Do not upload a paystub or enter identifying information.

2. Tax lines from your paystub

Enter employee amounts for this check, not year-to-date totals. A positive difference means your paystub withheld more than this model.

3. Deductions and reported net pay

Use traditional pre-tax 401(k) and eligible payroll HSA/FSA amounts. Include local taxes, disability/paid-leave deductions, garnishments, and all remaining deductions in Other deductions. Other pre-tax benefits or taxable noncash benefits can make the tax comparison unsuitable; the arithmetic check still helps reconcile cash amounts.

Match W-4 and year-to-date wages+

These optional entries affect only the estimate, not the arithmetic of your paystub. Use employer YTD FICA wages before this check. W-4 amounts are annual except extra withholding.

What this checkup can—and cannot—tell you

The arithmetic check answers a factual question: do the taxes and deductions you entered reconcile gross pay to the reported net amount? A non-zero gap usually means a paystub line was omitted, entered as a year-to-date value, or grouped differently by the employer.

The model comparison answers a different question: are federal withholding and FICA close to an estimate using your filing status, pay frequency, W-4 entries, and employer year-to-date wages? Your state tax is carried through to net pay, not checked against an independent model. Differences are a diagnostic starting point, not proof that payroll is right or wrong. State certificates, local taxes, taxable fringe benefits, imputed income, special wage treatment, and employer rounding can all create legitimate differences.

Two checks, two different standards

Arithmetic uses current-period gross minus every entered employee tax and deduction. The reported net pay should match that sum within one cent. The tool no longer rounds a negative reconstructed paycheck up to zero: deductions larger than gross remain visible so you can find a duplicated or misclassified line.

Tax estimates use wider, disclosed comparison thresholds because this is not your employer's payroll system. A tax line marked close to the model is not a compliance opinion. State withholding is deliberately not assigned a pass or fail; an unverified state formula could falsely flag a correct paycheck.

Reading the FICA lines

Social Security generally uses 6.2% of the check's eligible wages until this employer's cumulative wages reach the 2026 wage base of $184,500. Medicare generally uses 1.45% without that cap, with an additional 0.9% withheld on employer wages above $200,000. Enter year-to-date wages before—not including—the paycheck being checked. A full-year average can be wrong for the particular check that crosses a threshold.

Traditional 401(k) contributions usually reduce federal income-tax wages but not FICA wages. Eligible HSA/FSA contributions through payroll can reduce both. If the check includes other pre-tax benefits or imputed income, use the taxable wage bases in your payroll records and ask payroll to explain the treatment; this tool does not model every benefit plan.

How to investigate a difference

  1. Confirm that every amount came from the current-pay-period column, not the year-to-date column.
  2. Check whether gross pay includes taxable benefits, bonus pay, overtime, commissions, or imputed income.
  3. Compare the federal line with your current Form W-4 filing status, multiple-jobs selection, credits, other income, deductions, and extra withholding.
  4. Review state and local withholding elections separately; they do not necessarily mirror the federal W-4.
  5. Ask payroll to identify any remaining deduction or taxable-wage adjustment rather than emailing a complete paystub.

Official references