Publish every tax relief and exemption alongside the Budget, with five-year cost projections

HMRC administers approximately 340 tax reliefs and exemptions. They cost the Exchequer over £400 billion in forgone revenue each year. That is more than the entire NHS budget. Most of them are never reviewed, most are poorly targeted, and many have been in place for decades without anyone checking whether they still achieve what they were introduced to achieve.

Entrepreneurs Relief (now Business Asset Disposal Relief) was estimated by the IFS to have cost £22 billion over ten years with no meaningful evidence that it increased entrepreneurship. Patent Box costs roughly £1.2 billion a year and the evidence on whether it stimulated UK research rather than just relabelling existing activity is deeply mixed.

Require the Treasury to publish a full register of every tax expenditure alongside the main Budget document. Each entry must include: its original justification, its annual cost, its distributional impact, and an evaluation of whether it is meeting its stated aims. Any relief that has been in place for five years without evaluation should be marked as under review and subject to automatic sunset unless Parliament actively reconfirms it.

Tax expenditures are spending by another name. They should be scrutinised like spending. At the moment they are not.