What Barnett cannot tell you from Ayrshire

From Low Coylton the Scottish fiscal framework is not a seminar. It is the reason a council tax notice, an income-tax code and a waiting list can move in three different directions while London still talks about the UK public finances as if they were a single lever. Holyrood has income-tax rates and bands. It has a block grant, adjusted by a mechanism that is more interesting than the slogans attached to it. It does not have a gilt market of its own, a VAT base, or a central bank. That combination produces volatility that looks, from Westminster, like politics, and from Ayrshire, like arithmetic.

Barnett remains the starting point: a population-share of comparable English spending changes, not a needs formula, not a measure of rurality, not a theory of islands. The block grant adjustment then tries to make room for devolved income tax without double-counting. When Scottish income-tax receipts grow faster than the equivalent rUK base, Holyrood keeps the difference. When they grow slower, Holyrood eats the difference. A country with a different industrial mix, a different age structure and a different oil-and-gas residual will not track rUK pay forever. The framework assumes, for convenience, that it might.

Devolved tax is real. The hedge is not.

Income-tax devolution was sold as accountability. It is also a cyclical exposure. A slowdown that hits Scottish earnings harder than English ones does not wait for a White Paper. The Scottish Fiscal Commission exists precisely because someone has to say this out loud before the Budget for Scotland is written. The rest of the UK commentariat still treats that document as a local edition of the OBR. It is not. It is a forecast for a government that can move rates and cannot print sterling.

Holyrood can set a rate. It cannot set the risk-free rate. That asymmetry is the framework.

This matters for the Union argument, and it matters even if you wish the Union argument would go away. Any future settlement — more devolution, less, or independence — has to price the insurance that the current arrangement still provides: a central bank, a gilt market, and a welfare system whose balance sheet is UK-wide. People who want independence without that insurance should say what they are buying instead. People who want the status quo should stop pretending the adjustment mechanism is a technicality.

What the view from Ayrshire adds

South Ayrshire is not a residual of Edinburgh any more than it is a residual of London. Public-sector employment, a coastal visitor economy, a rural housing stock, and a labour market that loses graduates down the road to Glasgow: these are not captured by a Scotland-versus-England table. When inactivity is high in a travel-to-work area with thin private demand, a Holyrood tax cut does not conjure a shift. When house prices on the coast detach from local pay, a UK-wide housing speech does not reattach them.

The journal will keep writing about the framework because it is one of the few places in British public life where the words fiscal and constitution are forced to sit in the same sentence. They should sit together more often. A monetary union with asymmetric tax powers and a one-way insurance scheme is a design. Designs have failure modes. The failure mode here is not a dramatic split. It is a slow accumulation of adjustment bills that neither parliament wants to explain. Better to explain them from here, while the numbers are still on the page.

This essay is commentary, not advice. Sources: Bank of England, Office for National Statistics, House of Commons Library, Office for Budget Responsibility, Resolution Foundation. See the editorial method.