What is fiscal headroom?
Fiscal headroom is the margin by which the government is forecast to meet its own fiscal rules. It shows how much more it could borrow, or how much it could cut taxes, before breaking them. At the March 2026 forecast, the OBR put the Chancellor's headroom at about £24 billion.
Chancellors set fiscal rules, such as balancing day-to-day spending against tax income by a target year, and getting debt falling. Twice a year the independent Office for Budget Responsibility (OBR) forecasts whether those rules will be met. The gap between the forecast and the limit is the headroom. In March 2026 the OBR estimated it at about £24 billion, up around £2 billion. Headroom matters because it shapes what can go in a Budget. A small margin can vanish if growth or interest rates move the wrong way. Then a Chancellor may need to raise taxes or cut spending to stay within the rules. Critics say chasing a small headroom number leads to short-term decisions. The OBR publishes a fresh estimate alongside each Budget.
The left often argues the rules are too tight and stop worthwhile investment, and that more headroom should be used for public services.
The right often argues for a bigger buffer to reassure markets, and for using headroom on tax cuts rather than spending.
Britain is split. Now you decide.
In Population Decides' Budgets you see how each tax or spending choice eats into, or rebuilds, your headroom.
Play Population Decides freeCommon questions
Who decides the fiscal rules?
The Chancellor sets them. The OBR then judges whether the government is on track to meet them.
Why does headroom keep changing?
It depends on forecasts for growth, inflation and interest rates. Small changes in those can move headroom by billions.