Hunch. ONS figures from 21 October put UK rent growth at 3.81% before rounding, so rents must rise at least 0.34% in October alone for the figure to stay at 3.8%.
The 3.8% market resolves on the ONS release 'Private rent and house prices, UK: November 2026', due on 18 November 2026 at 9:30: YES if it prints UK rent growth in the year to October 2026 of 3.8% or higher, and NO if it prints 3.7% or lower, whatever happens to the September figure. If ONS moves the release, the market waits for a new date up to 2 December 2026 and is void after that, and Guardian or BBC reports of the same figure confirm it.
We looked for cases where ONS published a monthly figure for UK rent growth in the first six months of a law that made it easier for tenants to challenge a rent rise, in the largest part of the country only. The ONS figures start in January 2016. We found five such months, May to September 2026, all after England's new law, and checked whether yearly growth fell below the month before.