Our methodology
Our calculators deal with money, tax and major life decisions, so accuracy matters. This page explains exactly where our figures come from, how we test each tool, and what our calculators can and can’t do. If you ever find a number that looks wrong, please tell us.
The official sources we use
Every calculator is built from the rates, thresholds and formulas published by the relevant national authority for that market — not third-party estimates.
🇺🇸 United States
- IRS — federal income tax brackets, qualified-dividend rates, estate-tax exemption, FICA
- Federal Reserve — interest rates, the H.15 and G.19 releases
- Bureau of Labor Statistics — CPI/inflation and earnings data
- CFPB and SSA — consumer-credit guidance and Social Security
🇬🇧 United Kingdom
- GOV.UK & HMRC — Income Tax, NI, dividend allowance, SDLT, Inheritance Tax
- Bank of England — base rate and lending data
- ONS — inflation and earnings; MoneyHelper & the FCA for consumer guidance
🇦🇺 Australia
- ATO — income tax, PAYG, HECS/HELP, CGT, super
- RBA and ABS — cash rate, inflation and wages
- ASIC MoneySmart and state revenue offices — consumer guidance and stamp duty
How we build and test
- Built from primary sources. Each calculator implements the official formula and the current-year figures for its market.
- Automated checks on every change. Before anything ships, an automated suite boots every calculator and confirms the core results are finite and sensible, validates each page’s structured data and canonical tags, and checks every internal link resolves.
- Worked-example verification. We sanity-check results against the official authority’s own worked examples (for instance, a known estate or dividend scenario) so the numbers line up.
- Privacy by design. Calculators run entirely in your browser — your figures are never sent to a server or stored.
Update schedule
- Each tax year we update brackets, allowances and thresholds (e.g. the dividend allowance, nil-rate bands, the estate-tax exemption, FICA and personal-allowance figures).
- Rate-driven tools (mortgage, currency) use indicative or mid-market rates and clearly tell you to confirm a live rate before you transact.
- Each calculator shows the year it’s built for, and major pages carry a “last updated” date.
Limitations
Our calculators are for general information, not personal financial, tax or legal advice. They use standard assumptions and may not cover every edge case — complex estates, unusual income mixes, devolved-nation differences, or state-specific rules. For decisions that matter, confirm the result with the relevant authority above or a qualified professional.
Corrections & feedback
We take accuracy seriously. If you spot an error or an out-of-date figure, contact us and we’ll review and fix verified issues quickly. See also our about page and free embeddable calculators.