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.
Effective corporate tax rates
The OECD's own computed effective average and marginal corporate tax rates (EATR, EMTR) from Corporate Tax Statistics — not the headline statutory rate, and not something this site calculates. The two measures are ranked in separate sections, on the country-specific interest and inflation variant only.
Anti-avoidance regimes
OECD-recorded CFC rules, interest limitation rules, country-by-country reporting obligations and preferential IP regimes — four separate lists, each its own metric, with no jurisdiction ranked or ordered by how many of them it operates.
None of these five 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.