The Treasury had applied its usual scrutiny to the Programme’s Outline Business Case in 2020 and Full Business Case in 2023, approving each subject to conditions.80 The Treasury said it had been satisfied by the spend data in the business case it approved, but the NAO found that there were errors in the spend reported.81 The Treasury told us it had thought it had clarity on the programme spend when approving the business case, but between business case approvals it had less clarity over spend, the Treasury agreed that money spent on the Programme is not available for other public service.82 The Treasury noted that determining whether the programme is within budget depends on the plan being developed by NS&I.83