# Notes on building a position you can defend.

Short pieces from the team on sources, evidence and review: how the knowledge base is built, what a report owes its reader, and what we have learned reaching official texts that do not want to be read.

- [A regime election with a closing window: dating the Simples Nacional file before the window shuts](https://www.getax.io/blog/a-regime-election-with-a-closing-window-dating-the-simples-nacional-file-before.md) — Brazil's option into Simples Nacional runs on a fixed annual window and on clearing pending items first. For a founder who left Brazil but kept the operating company, the election memo has to carry a date and an evidenced pendency check. Here is where the window and the clearing condition live in the official text, and what the authority's notice does not settle about partners who are no longer resident. (Simples Nacional election · 15 October 2026)
- [Force of law, or reference only: reading the CBAM notices before you price a client's imports](https://www.getax.io/blog/force-of-law-or-reference-only-reading-the-cbam-notices-before-you-price-a-clien.md) — HMRC publishes the UK Carbon Border Adjustment Mechanism material as notices that carry the force of law alongside a reference document that explains them. A founder importing goods will not see the difference, and an adviser who quotes the explanatory text is defending a sentence that creates nothing. This is a source walk through where the obligation actually lives, what the notices leave to later publication, and what we do not yet know. (CBAM notices · 12 October 2026)
- [The worst number we ever measured](https://www.getax.io/blog/the-worst-number-we-ever-measured.md) — Measured against naive AI models: from 24% to 98%. We kept our worst number, shipped nothing, and rebuilt — the short version of that road, and why the model was never the product. (Accuracy · 22 September 2026)
- [Absence is information](https://www.getax.io/blog/absence-is-information.md) — A knowledge base that only records what exists misleads by omission. Why getax records the taxes a country does not levy as facts in their own right, and why a gap it cannot yet fill is shown rather than hidden. (Coverage · 3 September 2026)
- [Tier-one evidence, and why a summary is never a source](https://www.getax.io/blog/tier-one-evidence.md) — Commentaries, firm bulletins and encyclopaedias are useful for finding a rule and useless for proving one. How getax ranks evidence, why a rate can only be validated on the authority's own text, and what that costs. (Sources · 3 September 2026)
- [Why every number in a getax report carries a citation](https://www.getax.io/blog/why-every-number-carries-a-citation.md) — A tax position is only as defensible as its weakest sentence. Here is the chain each figure in a getax report has to pass through before it can appear in one, and what it means that a claim is never a fact until a council rules. (Provenance · 3 September 2026)