Sources and how we check

Numbers and rules come first from public data of government agencies, state-owned utilities and the law database.

When data has no official source, the page names the website or brand it comes from. News reports are only leads, never the only source.

The “Sources” list on each page gives the source name, the publisher and the date we checked it.

An AI that did not help make the page does the check (an independent Claude agent, or Codex, by OpenAI).

• List each statement on the page: numbers, units, periods of application and conditions.
• Open the official source and find the matching text.
• Mark each item: correct, wrong, out of date, or cannot confirm.

• Wrong or out of date: we correct it. If the checker is wrong, we must quote the official text to reject its finding.
• Cannot confirm: we add an official source, change the statement to “this tool's assumption”, or remove it.
• After the corrections, we run the calculation tests and work out at least one case by hand. When an official calculator exists, we compare the results with it.

When “How we made this page” says that a different AI model (Codex) or a separate, independent AI agent (Claude) checked the page against the sources, the page went through the steps above. The date after it is the check date.

When it says the page is not yet independently checked, the page has not been checked.

An AI model does the check. It is not a human review. AI can make mistakes.

Some official websites block automated access. Then we open the source in a browser to check it.

Rules can change after the check date. The latest notice of the competent authority applies. If you find a mistake, see corrections and contact.