As its compliance productivity had fallen, we asked HMRC whether it could reassure us that it was delivering value for money. It said when it brings in new compliance resource it expects to see a dip in productivity before recovering. HMRC told us this was because new staff are not as productive as experienced staff; it has to move existing staff away from frontline work to mentor and support new staff; and every time it adds compliance resource, the marginal rate of return of the new resource will probably be lower as it is already working the cases that have the most potential to generate yield. HMRC acknowledged that it has to get productivity “back up to the levels that our experienced staff have had before”.41 HMRC’s legacy IT systems and systems for interacting with customers