When we examined DWP’s 2021–22 accounts, it told us about another category of historical State Pension underpayment caused by gaps in the National Insurance records of women who had previously claimed Child benefit.29 DWP and HMRC explained to us that between 1978 and 2000, people claiming Child Benefit should have automatically received Home Responsibilities Protection (HRP), which lowered the National Insurance contributions needed to receive a full State Pension.30 Up until 2000, the body responsible for Child Benefit did not record a National Insurance number as part of a claim. This led to missing periods of HRP on the National Insurance records of some women and thus an underpayment of State Pension, which is calculated based on National Insurance contributions.31 This is not the first time that DWP has encountered an issue with missing periods of HRP. In 2010–11 DWP worked with HMRC to pay £84 million in arrears to pensioners for the same issue.32 DWP admitted that it was “assumed that the situation had been addressed and solved”.33