Recommendation 28

A significant task for HMRC is to move taxpayer data from its old Self Assessment system to its new tax system. HMRC told us that its old legacy systems hold records in a fundamentally different way, and it had expected the conversion into the new system to be simpler than it proved to be for VAT. HMRC had learned this from its experience from the programme’s rollout for VAT and had then had to change its assumptions as it moved towards planning the Self Assessment phase. HMRC told us it was expecting that at least 30% of its Self Assessment taxpayer records would need manual work in order to ensure taxpayer data were moved to the new system correctly. HMRC had not yet started the data migration for Self Assessment, but it was planning to move 1.6 million taxpayer records—which covers the first two cohorts for Self Assessment—before those taxpayers start enrolling on the Making Tax Digital programme.68 Working with software providers