Fintra Payroll
A payroll tax engine you can actually audit
Paycheck Trace
Example figures- GROSS
- $4,807.69
- this period
- TAXES
- $1,142.06
- FIT+FICA+state
- NET
- $3,241.13
- after deductions
- FIT: Pub 15-T Worksheet 1A
- $612.40
- Social Security: 6.2% (cap tracked)
- $298.08
- Medicare 1.45% + Add’l 0.9% over YTD
- $69.71
- Invariant: gross = net + tax + deductions
- pass
What the tax engine computes
Fintra’s tax engine turns an employee’s earnings, W-4, and pay frequency into a fully-traced paycheck. Every step is deterministic: the same inputs always produce the same cents, and every rate comes from a versioned database table with an effective date, a source citation, and a verified flag: never from an AI guess.
| Tax | Basis | Detail |
|---|---|---|
| Federal income tax | Pub 15-T percentage method | Worksheet 1A: annualize, then offset, then schedule, then de-annualize, then credits, then extra withholding |
| Social Security | 6.2% to the annual wage base | YTD wage-base cap applied straddle-exact |
| Medicare | 1.45% of Medicare wages | No wage cap |
| Additional Medicare | 0.9% over $200,000 YTD | Threshold tracked on YTD Medicare wages |
| FUTA | 0.6% to $7,000 (after 5.4% credit) | Employer-side; full credit assumed |
| SUI/SUTA | Org-configurable rate + wage base | Per-state employer unemployment |
A calculation trace on every paycheck
Each check stores a per-tax trace (base amount, rate, rate-year, YTD-before, and whether a cap applied) plus an internal invariant self-check that asserts gross equals net plus taxes plus deductions plus garnishments before the check is ever saved.
What you can prove after the fact
- Which rate year and source produced each rate
- The exact taxable base after pre-tax deductions
- Whether a Social Security or FUTA wage-base cap was hit this period
- That the paycheck balances to the cent
Fail-closed rate safety
An independent reference implementation of federal withholding is property-tested to agree with the production engine to the cent: a second pair of eyes on the most error-prone math in payroll.
Inside Fintra
The engine feeds every downstream surface: pay stubs, remittance liabilities, year-end W-2 boxes, and the GL export: all derived from the same traced numbers.
Questions people ask
Where do the tax rates come from?
Every rate lives in a versioned database table with a rate year, effective date, source citation, and a verified flag. There are no AI-sourced rates; refreshing re-seeds from the built-in provider and logs the change.
Is the 2026 tax year supported?
Yes. Statutory FICA/FUTA for 2026 always compute; 2026 federal income-tax withholding (transcribed from Rev. Proc. 2025-32) is owner-activated by default pending CPA sign-off and is reversible per-org.
What is the calculation trace?
A structured record stored on every paycheck showing, for each tax, the base, rate, rate-year, YTD-before amount, and whether a wage-base cap applied, so any figure can be justified later.
How does Fintra avoid rounding drift?
All money is handled as integer cents with a single rounding rule, and an invariant self-check asserts the paycheck balances before it is saved.
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Payroll math you can defend
Explore the deterministic, fully-traced tax engine behind every Fintra paycheck.