The United Kingdom’s Retail Price Index (RPI) accelerated to 3.9% year-over-year in September 2026, up from 3.4% in August 2026, according to data updated on 21 October 2026. The reading points to a re‑acceleration in price pressures after a period of relative moderation in the headline RPI measure.
On a year-over-year basis, the September figure compares the change in prices to September a year earlier, while the August reading reflected a comparison to August of the previous year. The move from 3.4% to 3.9% suggests that, at least for now, disinflation momentum in the UK’s broader retail price basket has paused, a development that could factor into market expectations around future interest-rate and cost-of-living dynamics.
The RPI, while less commonly used than the Consumer Prices Index (CPI) for official targets, remains influential for certain contracts, index-linked securities and wage negotiations. The latest increase may therefore have knock-on implications for households and sectors where payments and adjustments are tied to RPI-linked formulas.
