Rankings
This index does not compute a composite “enforcement score” — definitions of an audit, a risk assessment or an AI use case differ too much between administrations for that to mean anything. Instead, each ranking below is a single metric from a single dataset, with its source and its limits stated up front.
Tax burden
Total tax revenue as a share of GDP, general government, from OECD Revenue Statistics Global — plus VAT reliance, the biggest risers and fallers since 2000, and the highest headline statutory rates. Two different tax-to-GDP definitions (OECD general government vs. IMF/World Bank central government) are shown separately and never mixed.
Enforcement intensity
Audit hit rates and additional assessments raised, as a share of tax collections, from the International Survey on Revenue Administration (ISORA). These are self-reported by each administration, not independently measured — read a high or low figure as a statement about how that authority describes its own audit programme.
AI adoption
Which tax administrations told the OECD they use artificial intelligence, and what for — fraud and evasion detection, or final administrative decisions — from the Inventory of Tax Technology Initiatives (ITTI). Self-reported answers, reproduced as given.
None of these three measures the same thing, and none should be read against the others. Where a ranking is self-reported by the administrations it describes, that is stated on the page itself, not buried in a footnote.