Abstract Against the background of record levels of UK hydrocarbon production and a government review of the UKCS tax regime, this paper provides evidence that the government’s share of UKCS profits is very low by historical and international standards and demonstrates that the current tax regime is extremely weak. The justification for the latter is then challenged by assessing the relative profitability of UKCS companies, using data from UK national accounts and from Form 10-K and Form 20-F company reports and analysing both accounting profits and forecast discounted cash flow. This shows that companies operating on the UKCS enjoy substantially higher profitability relative to both other UK companies and other oil and gas provinces elsewhere in the world. Further evidence of the weakness of the UK regime is provided by a comparison with the Norwegian oil and gas tax regime. The paper therefore makes a strong case for the reform of the UKCS tax regime.