Original sources first
We prefer primary government data, original research documents, and official explanations. A competitor calculator can help us understand a user journey, but it is not treated as authoritative evidence for a numeric default.
Numeric reference values carry a source, date or period, retrieval date, unit, and explanation of what the value represents. Undated source pages are identified as undated.
Examples are not averages
Prefilled calculator amounts are illustrative examples unless a field explicitly names a source. Fees and optional expenses may be zero. We do not present personal estimates as national facts or imply that a benchmark is the right answer for every household.
Review and corrections
Calculation changes require relevant tests before release. Source snapshots are reviewed when updated; electricity data is flagged after 120 days from release. Review dates reflect an actual review, not the date a page happened to rebuild.
Reported formula problems, stale defaults, confusing wording, and accessibility issues are checked against reproducible examples. Material corrections are described in the correction log.
Commercial independence
Advertising and remote analytics are disabled in this release. If advertising is introduced later, placements must remain distinct from controls and results, and privacy disclosures must be updated first. Rankings, traffic, and rich search results are not guaranteed.
Reviewed September 5, 2026.