Question to the HM Treasury:

To ask His Majesty's Government what changes they have made over the past five years in the application of comparability factors to the Barnett formula for determining cash payments to the Welsh government consequential to expenditure on railway services located solely in England.

Comparability factors are used to determine the extent to which a UK Government department’s spending is comparable (where policy is devolved) to the Welsh Government.

Comparability factors are generally updated prior to each spending review. In the past five years, the Department for Transport’s comparability factors were updated at the Spending Review in 2020 and again at the Spending Review in 2025. The most recent comparability factor applied to changes in the Department for Transport budgets at the Spending Review in 2025 was 33.5% for Wales. A comparability factor of 36.6% was applied at the Spending Reviews in 2020 and 2021.

Full details of changes to comparability factors over the past five years, including those for the Department for Transport, are published in the relevant Statement of Funding Policy:

https://assets.publishing.service.gov.uk/media/684859e3d0ca5d7801e4e6f6/Statement_of_Funding_Policy.pdf