The Sunday Times Rich List 2025 listed 156 billionaires, compared with 165 last year. We asked HMRC if it has ever tried to link the Sunday Times Rich List with its own records to estimate how many billionaires on the list are tax resident in the UK. HMRC told us that it has access to a huge range of internal and external data which it uses to identify wealthy individuals, cross-check across data sources, and target its compliance work as effectively as possible but it would not be drawn on the use of specific data.30 We understand that in the United States, the Inland Revenue Service has worked with researchers to link its data to the Forbes 400 list, their equivalent of the Sunday Times Rich List. We asked HMRC if it would allow academics to do something similar with its data. HMRC agreed 25 C&AG’s Report, para 2.14 26 Qq 120-122 27 Qq 21-22, 25-26, 28-30 28 Q 35 29 Q 120 30 Qq 31-33 12 that, in theory, it would be possible for academics to use its Datalab to securely access its data for research purposes and use other information to do analysis.31