We challenged the Department on the adequacy of its quality assurance mechanisms.18 Despite the complexity of State Pension entitlements and the increased risk posed by manual processes of calculating an award, the Department’s own internal analysis found that existing quality checks failed to identify the systematic underpayment of thousands of pensioners.19 There are three levels of quality assurance in State Pension. The quality of a caseworker’s work is assessed by team leaders (Tier 1) and by a central team (Tier 2). The rate of official error is assessed as part of estimating fraud and error across all benefits (Tier 3). However, as the NAO found, “since 2009, Tier 1 and Tier 2 processes focussed on checking changes to case details, such as a change of address or the death of a spouse, rather than the overall accuracy of the payments; and the small sample sizes of Tier 2 and Tier 3 relative to the basic State Pension caseload made it difficult to identify the errors”. In addition, conversations with caseworkers as part of the NAO investigation showed they feel that the Department has too few staff trained on State Pension processes to manage the caseload and perform the expected quality assurance procedures.20It is a fundamental principle of financial control and assurance that more attention should be focussed on those areas where there is intrinsically a higher risk of failure due to human error. The Department failed to apply this principle here even though it was aware of the system’s very high vulnerability to human error.