How we maintain accuracy across 8 country tax regimes
This page documents the sourcing, freshness, and editorial process behind every calculator on 3tej.com. We publish it openly so readers, regulators, and reviewers can audit our claim that the numbers are current and correct.
1. What counts as a primary source
A calculator's underlying rate, threshold, or bracket is only ever taken from the relevant tax authority's own publication, not from third-party blogs or AI summaries. We cite the publication by name and number so any claim is auditable. The table below lists the canonical source for each country we cover.
| Country | Authority | Publication | Data as of |
|---|---|---|---|
| US | Internal Revenue Service | Publication 17 (2026) | Mar 1, 2026 |
| US | Internal Revenue Service | Notice 2026-12 (retirement contribution limits) | Mar 1, 2026 |
| US | Social Security Administration | COLA fact sheet (2026) | Mar 1, 2026 |
| UK | HM Revenue & Customs | PAYE Tax Tables 2026-27 | Apr 6, 2026 |
| UK | HM Revenue & Customs | Income Tax rates 2026/27 | Apr 6, 2026 |
| CA | Canada Revenue Agency | T4032 Payroll Deductions Tables 2026 | Jan 1, 2026 |
| AU | Australian Taxation Office | Individual income tax rates 2026-27 | Jul 1, 2026 |
| DE | Bundesministerium der Finanzen | Einkommensteuer 2026 Tabelle | Jan 1, 2026 |
| IN | Income Tax Department, Govt of India | Income-tax Act FY 2026-27 | Apr 1, 2026 |
| SG | Inland Revenue Authority of Singapore | YA 2026 individual income tax | Feb 1, 2026 |
| AE | UAE Ministry of Finance | Federal Decree-Law No. 47 of 2022 (Corporate Tax) | Jan 1, 2026 |
Secondary sources (specialist journals, professional-body explainers, qualified accountants) are consulted only to interpret the primary source when its wording is ambiguous. They are never the basis for a rate.
2. How we refresh the numbers
Every locale has a known annual rate-publication date (IRS Notice in late autumn, HMRC tables on 6 April, ATO TaxTime on 1 July, BMF and CRA by 1 January). We track those release calendars and update within ten working days of each new publication. The freshness stamp on each calculator names the source the data came from and the date we last reconciled it.
Update cadence by locale
- US - annual IRS revenue procedure (RR/RP) for inflation-adjusted brackets, late November; SSA COLA early October; standard mileage early December.
- UK - HMRC PAYE tables on 6 April; HMRC manuals on a rolling basis tracked via the GOV.UK PAYE publications RSS.
- Canada - CRA T4032 on 1 January; provincial budgets in March/April; CPP/EI rates first business day of each year.
- Australia - ATO TaxTime release on 1 July; Stage 3 cut integration tracked from Treasury legislation, not media.
- Germany - BMF Einkommensteuer-Tabelle on 1 January; Sozialversicherungswerte (Bemessungsgrenzen) published in Bundesgesetzblatt each autumn.
- India - Union Budget on 1 February; Finance Act enacted by 31 March; CBDT rules tracked via incometaxindia.gov.in.
- Singapore - IRAS YA forms in February; CPF rates each January via cpf.gov.sg.
- UAE - MoF Federal Decree-Law amendments via mof.gov.ae; FTA Cabinet Decisions tracked via tax.gov.ae.
3. How calculations are built
Each calculator is implemented in plain JavaScript that ships with the page and runs entirely in your browser. The formula is documented inside the same file as the UI, and the rate constants are exported from one named module per country so the audit trail is mechanical.
- One module per locale, one constant per rate. Constants are never inlined into UI code.
- Each constant carries the source citation and the date it was reconciled, in a JSDoc comment above its declaration.
- A diff that changes a rate must also bump the citation date. CI checks this before merge.
- Unit tests verify the calculator against worked examples taken directly from the primary source (e.g. IRS Pub 17 Appendix A; HMRC PAYE 2026/27 Manual Example C).
4. Fact-check and review process
No tool or article goes live unsigned. The minimum process is:
- Drafted by an editor named in the byline.
- Source-checked against the cited publication. The reviewer signs off the same way they would for a regulated-industry publication.
- Worked example compared against the official source's own worked example, where one exists.
- Annual recalibration after each rate-publication cycle. The reconciliation date is updated on the page footer.
Anything we cannot source confidently is not published. We would rather omit a calculator than launch one whose rates we cannot defend.
5. Independence and funding
3tej is privately funded by its founder. We do not accept guest posts, sponsored calculators, or paid placements. Affiliate links, where used, are disclosed inline and do not influence which tools or methodologies we feature. We do not provide personalised financial, legal, or medical advice; every page carries a disclaimer to that effect.
6. Errata and corrections
When we get something wrong, we fix it on the page and append a dated correction note. Significant errors (anything affecting a calculated output) are logged in the public errata list. Suspected errors can be reported to hi@3tej.com, or via the comment box at the bottom of any tool / blog post; corrections-class reports are prioritized in moderation.
Editorial team
The humans accountable for the content on 3tej: About the editors.