Accuracy is the product
Tax figures that are wrong cost real people real money. So this site runs on a simple protocol — and publishes it, so you can hold us to it.
The protocol
- Primary sources only. Every number, threshold, and rule comes from an IRS source document — a fact sheet, the final form, or an official IRS list — never from another calculator site.
- Cited where it appears. Each tool names its IRS source next to the result, not buried on a central page.
- "Last verified" dates. Every tool shows the date its rules were last re-checked against the source.
- Tested formulas. The shared calculation module is automatically tested against the IRS's own worked examples (including the FS-2026-13 Q16 double-time example and the Q21/Q22 W-2 examples). A failed test blocks changes.
- Public corrections. If we get something wrong, the fix is recorded in the corrections log below with a date — not silently edited.
- Nothing invented. Where the IRS has not settled a point, the tools say so instead of guessing. (Example: we state the SSTB exclusion for tips plainly from FS-2025-03 and do not model any claimed transition relief we could not confirm in a primary source.)
Sources used on this site
| Source | What it establishes | Used by |
|---|---|---|
| IRS Fact Sheet FS-2026-13 (August 2026) — irs.gov/pub/taxpros/fs-2026-13.pdf | Qualified overtime rules: only the FLSA-required premium counts (Q1); double-time and holiday/weekend premium treatment with a worked example (Q16); mandatory Box 12 code TT reporting from 2026 (Q6, Q10); the reported-amount ceiling (Q20); overstated amounts (Q21); the Form W-2c fix and employer-refusal outcome (Q22); Form 4852 cannot be used (Q23); exempt employees and 20% employee-owners (Q4–Q5); joint filing and SSN rules (Q24–Q25). | Checker, Overtime calculator, Hub |
| Schedule 1-A (Form 1040), final 2025 form — irs.gov/pub/irs-pdf/f1040s1a.pdf | The form's own arithmetic: MAGI (Part I, line 3); tips cap and phase-out (Part II, lines 7–13); overtime cap and phase-out (Part III, lines 15–21); car-loan cap and its round-up phase-out (Part IV, lines 24–30); senior 6%-of-excess phase-out (Part V, lines 31–37); total (line 38) to Form 1040 line 13b. | All calculators, Helper |
| IRS Fact Sheet FS-2025-03 (July 2025) — Working Families Tax Cuts deductions | All four deductions and eligibility: tips SSTB exclusion; car-loan loan/vehicle rules (originated after 12/31/2024, new vehicle, personal use, first lien, U.S. final assembly, VIN); senior age-65 rule and per-person $6,000; joint-filing and SSN requirements. | Tips calculator, Helper, Hub |
| IRS Schedule 1-A explainer (FS-2026-04, March 2026) — irs.gov newsroom | Who can use Schedule 1-A; the four deductions and caps; itemizing not required; Part-by-Part completion rules. | Hub, Helper |
| IRS Treasury Tipped Occupation Code list — Occupations that customarily and regularly received tips | The 71 occupations (with TTOC codes) in which tips can be qualified tips, in 8 categories. | Tips calculator |
| IRS Fact Sheet FS-2026-01 (January 2026, superseded by FS-2026-13) — Questions and answers, overtime deduction | Tax year 2025 transition rules: no separate reporting required for 2025; workers may use Notice 2025-69 methods and the Schedule 1-A instructions to calculate amounts from their own records (Q6–Q7). | Checker (2025 branch) |
What we label as estimates
Two things on this site are not IRS figures and are always labelled: (1) the "estimated tax saved" line, which simply multiplies your deduction by the marginal rate you enter — a modelling aid, not a prediction; and (2) the checker's "plausible" band, which is our plain-English way of saying a small difference is likely rounding or pay-period timing. Everything else traces to the sources above.
Corrections log
| Date | Correction |
|---|---|
| — | No corrections yet. This log starts on launch day and every fix will be recorded here, dated, with what changed and why. |
Spotted something that looks wrong? Compare it against the IRS source linked beside it — and if we still have it wrong, that is a correction-log entry waiting to happen. Contact details will be published here at launch.
Estimates only — not tax advice. This site provides general information about IRS rules. It is not a substitute for the IRS instructions or a qualified tax professional.