Retail Prices Index
UK Consumer Price Index, published by the ONS, that still sets index-linked gilt payments.
A 0.3% rise in the Retail Prices Index added £2.1bn to UK debt interest in August 2026 through index-linked gilts, the ONS said on 22 September, taking interest to £8.8bn, the highest for an August on record.
Last refreshed: 7 October 2026
Timeline for Retail Prices Index
Mentioned in: 30-year gilt passes 6%, last seen 1998
Is Britain Actually Broke?Mentioned in: ONS puts borrowing £8.1bn over OBR path
Is Britain Actually Broke?Background
The Retail Prices Index (RPI) is a measure of consumer price inflation produced by the Office for National Statistics. The UK Statistics Authority removed its National Statistic designation in March 2013, after an assessment found that its formula did not meet international standards. The ONS still publishes it because index-linked gilts are tied to it.
In August 2026 a 0.3% rise in the RPI added £2.1bn to debt interest through index-linked gilts, helping push interest to £8.8bn, the highest for an August on record.
The UK Statistics Authority and HM Treasury confirmed in November 2020 that the RPI will take on the methods and data sources of CPIH from February 2030. Until then, RPI movements feed straight into the cost of the government's index-linked debt.
The index still sets debt interest
The Office for National Statistics reported on 22 September 2026 that debt interest reached £8.8bn in August, the highest for any August on record. Of that, £2.1bn came from a 0.3% monthly rise in the RPI, which lifts the payments on index-linked gilts.
Debt interest ran £2.0bn above the Office for Budget Responsibility's forecast for April to August. With benefits, it was one of the two largest items in borrowing that finished £8.1bn over the OBR's profile. The August figures show why an index stripped of its National Statistic status in 2013 still moves the public finances every month.