Higher gilt yields, rate expectations and inflation could have eroded up to £15bn of the Chancellor's room for manoeuvre since March, Philip Shaw estimates in City AM.
In a piece published on 23 October, he writes that March's forecasts implied a buffer of £24bn against the current-budget surplus rule and £27bn against the debt rule. The £24bn figure is consistent with the £23.6bn of headroom at the March fiscal update and with the Resolution Foundation's estimate of spring headroom.
Shaw also says next year's shift in the fiscal target year could improve headroom by £6.7bn. He bases that on the 2026 Spring Forecast.
He notes that the OBR's 1.1% growth projection for this year looks low. He adds that inflation looks set for an upgrade this year and next.
These are one analyst's estimates, not OBR or Treasury figures. The Resolution Foundation said on 13 October that headroom may have fallen to as little as £12bn.