Barnett formula

The Barnett formula is the mechanism by which the UK Treasury calculates the block grants paid to Scotland, Wales, and Northern Ireland. Devised by Chief Secretary to the Treasury Joel Barnett in 1978, it adjusts devolved budgets based on per-Capita changes in comparable English public spending. If England increases NHS spending by £1 billion, Scotland receives a population-proportionate share automatically, regardless of local need. The formula has never been enshrined in statute and operates by Treasury convention.

In the 2026 Holyrood election, the formula became politically salient because Scottish income tax changes interact with it via the block grant adjustment: if Scotland raises or cuts income tax, the Treasury offsets the block grant by a corresponding amount to avoid double-counting. This mechanism is the basis for the IFS critique of the Scottish Conservative manifesto, whose pensioner tax cut yielded less fiscal space than the headline cost implied. More broadly, all five Scottish Holyrood parties received IFS verdicts of fiscal incredibility in 2026, a devolution-era first.

The Wales angle has sharpened in May 2026. Rhun ap Iorwerth's six-demand priorities statement explicitly included a fair funding formula, framing Barnett as needs-blind and calling for a replacement based on relative deprivation and public service demand . The Welsh Government has made similar arguments since the 2010s, but a Plaid First Minister with a confidence-and-supply arrangement that required no Labour votes makes the ask harder for Westminster to dismiss as routine Welsh Labour positioning. Reform UK has separately attacked the formula from an English-taxpayer framing, arguing it represents unfair subsidy of devolved nations, pressure from a different direction that leaves the Treasury defending the status quo on two flanks simultaneously.