The UK borrowed £1.8 billion in July, according to the Office for National Statistics, £0.7 billion more than in July last year and £2.3 billion above the Office for Budget Responsibility's forecast. July is a month the Treasury normally enjoys, because the self-assessment deadline pulls in a year of income tax from the self-employed and from people with investment income in a single lump.
What the number measures
Public sector net borrowing is the gap between what the state spends and what it raises in taxes and other receipts in a given month. When spending is higher, the state issues gilts to cover the difference. It is not the same as the debt: borrowing is the flow each month, debt is the stock that has built up over decades.
The stock is now £2,984.9 billion, just under £3 trillion, or 94.1% of GDP. That ratio is 0.8 percentage points lower than a year ago, which is the one genuinely favourable line in the release: the economy has been growing slightly faster than the debt.
Where the pressure is
Two figures do most of the work. The first is debt interest, which came to £7.7 billion in July, up 9.6% on a year earlier. The ONS attributes £1.3 billion of that to the capital uplift on index-linked gilts, the portion of government debt whose principal rises with the retail prices index. That is the mechanical part of the bill: when RPI moves, the amount the state owes on those bonds moves with it, without any new borrowing taking place.
The second is the cumulative overshoot. Borrowing in the financial year to July was £56.7 billion, £6.0 billion less than the same four months last year but still £2.3 billion above the OBR's profile. A shortfall against forecast that neither widens nor closes month after month is the pattern that matters for a Budget, because the OBR's next forecast has to start from the actual outturn rather than the plan.
Why it matters for October 28
Healey has set his first Budget for October 28. British fiscal rules work by requiring the OBR to certify that the government is on course to meet its targets in five years' time, and the margin by which it does so is the "headroom." Headroom is what allows a chancellor to spend or cut taxes without breaking a rule. When borrowing runs above forecast and debt interest runs above forecast, headroom shrinks before a single policy decision is made.
That is the constraint the July data tightens. It does not, on its own, force any particular choice. Whether the response is higher taxes, lower departmental spending, a revision to the fiscal rules themselves, or a bet that growth will do the work, is a political decision that will be made in October and not one this release settles.
For gilt investors the relevant question is narrower: how much the Debt Management Office will need to issue, and at which maturities. Long-dated government bond yields have been under pressure across developed markets this month, with the US 30-year at 5.24% on Thursday after the Treasury announced it would double its buybacks of long-dated debt. A Budget that increases the projected supply of long gilts matters more to that market than the headline borrowing number does.
One caution on reading a single month. Monthly public finance data is noisy, revised routinely, and distorted by timing effects in both receipts and spending. The £2.3 billion miss is real, but it is the run of months rather than July alone that will shape the OBR's October forecast.
