UK Audit Finds £18.6 Billion in Overdue Tax Outside Payment Plans as HMRC Faces Collection Limits

Britain's tax authority has made measurable progress in reducing overdue tax as a share of receipts, but an October audit reveals that its hardest-to-collect debts have grown sharply. The distinction matters: a smaller debt ratio does not necessarily mean the government has solved the backlog of older, increasingly difficult cases.

The National Audit Office reported on October 23, 2026, that HM Revenue and Customs was owed £43.8 billion at the end of the 2025–26 financial year, equivalent to 4.7% of tax receipts. That ratio had declined from 5.6% in 2022–23, and the auditors credited changes to collection staffing and data use for part of the improvement. Yet debt older than one year and not covered by an agreed payment plan reached £18.6 billion, compared with £5.3 billion before the pandemic.

The audit's collection figures show why age matters. HMRC estimates that 46% of the outstanding £43.8 billion may not ultimately be recovered. That is a forward-looking estimate about debts still on its books, not an assertion that 46% has already been written off. The department handled £103.6 billion in newly arising tax debt during 2025–26, about twice the annual average in the five years before the pandemic.

Independent reporting by Business Matters examined £12.9 billion in revenue losses recognised in 2025–26, including £9.8 billion of write-offs associated with company closures and personal bankruptcies. These recognised losses must not be added to the forecast 46% unrecoverable share as though they describe two independent losses. The same reporting noted that business insolvencies increased 39% between 2019–20 and 2025–26, with pandemic-era insolvency backlogs contributing to the change.

The watchdog also documented results from earlier investments. Measures introduced since 2021, including additional collection staff, greater use of private debt agencies and better debtor segmentation, were estimated to have generated £10.7 billion in additional revenue against £368 million spent. The NAO credited this progress while warning that adding more staff alone would deliver diminishing returns because remaining cases tend to be smaller or harder to resolve.

The NAO recommends that HMRC reduce inefficiencies in its processes and systems, make digital payment plans easier to manage, and evaluate which interventions work best for different taxpayers. A new case-management system is among the planned improvements, but auditors say the department needs to manage implementation risks and focus on the productivity of existing staff.

HMRC told Business Matters that it welcomed the report's recognition of progress and was supporting people who owe tax while taking enforcement action against those who decline to engage. That response is relevant because overdue tax can reflect insolvency, cash-flow constraints or late payment; it is not synonymous with evasion or fraud.

The public-interest test now is whether the authority can convert its recent ratio improvement into fewer old, unmanaged cases without misrepresenting accounting losses or overpromising recoveries. The audit supplies a measurable baseline, but it does not establish that all uncollected tax could realistically be recovered or that a specific amount was lost through misconduct.