Debt interest cost about £2bn more than the OBR forecast in September, while tax receipts ran ahead of forecast, according to City AM analysis of the latest ONS figures and Resolution Foundation research.
Debt interest was £10.9bn in September, up around 17% on the same month last year. Receipts were 9% higher than in September 2025, driven by stronger than expected corporation tax, the Resolution Foundation found. City AM argues that this makes spending, not tax receipts, the Treasury's problem.
The OBR's current forecast puts debt interest at just under £110bn this year, rising to nearly £135bn in 2030. On that forecast, debt interest overtakes the combined Home Office, justice and defence budgets in 2028-29.
Existing OBR analysis, cited by City AM, shows how sensitive the figures are to markets. Each sustained one percentage point rise in gilt yields costs about £8.4bn by 2030. If inflation and short term interest rate expectations also rose by one point each, the cost to headroom could reach £23.8bn. These are not new OBR forecasts.
Headroom against the main fiscal rule was about £23.6bn in March. City economists widely expect it to be about £12bn now, City AM reports. That estimate has not been independently checked.
Ruth Gregory of Capital Economics described the public finances data as a "dismal picture".