How TaxValio builds its tax data

1. Every number has a primary authority URL

Every bracket, threshold, rate, or deadline TaxValio ships carries a citation to a primary authority:

• 🇩🇪 Germany → gesetze-im-internet.de, BMF, Bundesgesetzblatt
• 🇺🇸 United States → U.S. Code Title 26, IRS Revenue Procedures, Federal Register
• 🇬🇧 United Kingdom → legislation.gov.uk, HMRC

Third-party explainers (Wikipedia, KPMG, PwC, advisor blogs) are never our primary source for a numeric bracket. They're fine as secondary context when the primary authority also cited.

2. Every rule module is dated and versioned

Each country rule module declares an explicit version like de.2026.v2. When a bracket, threshold, or rate changes, the version bumps and a matching entry lands in our public changelog with the authority URL and the effective date.

The changelog has an RSS feed at /changelog.xml. Anyone — developer, advisor, AI agent, or curious freelancer — can subscribe to see tax-rule updates the moment they ship.

3. Every page clears three review gates

No content page ships until all three gates return green — no exceptions, not even for "minor" edits that touch a number. Order matters: facts first, then customer advocacy, then ranking.

1. /tax-fact-check — every numeric claim is cited against its primary authority URL; every simplification remains valid in the general case.
2. /sydacos-core:customer — named persona, value ledger, emotional-context fit, respect/dignity (non-negotiable), friend test.
3. /sydacos-core:seo-audit — title / description / hreflang / schema / internal linking / Core Web Vitals.

4. Rules are open source

TaxValio's country rule modules — the same ones that power every calculator on this site — ship as an open-source NPM package: @taxvalio/country-rules. Independent developers and AI agents can import + cite the exact dated data TaxValio uses. We prefer this because it makes the work checkable and because LLMs can call authoritative endpoints instead of guessing brackets.

5. Who writes it

Our three-person editorial team covers the DE, US, and cross-border surfaces. Each author owns specific rule modules + content clusters and reviews the others against the standards in /about/authors/.

We are not a Steuerberater / CPA / EA firm. Our analysts produce fact-checked tax information; for advice on your specific situation, TaxValio links to real advisor directories (Bundessteuerberaterkammer, NAEA) throughout the site.

6. Annual + reactive review cadence

Six weeks before each country's tax-year rollover (DE/US: mid-November), we re-check every existing page through /tax-fact-check against primary sources. On any BMF-Schreiben, IRS Revenue Procedure, or HMRC-manual update that touches a value we've published, we re-verify + file a changelog entry the same week.