OBR October 2026: risks and assumptions behind the forecast headline

Key facts

Each row is checked against the stored copy of the official document; open a row to see the exact words and where they appear.

The story

The Office for Budget Responsibility (OBR), the independent forecaster for the public finances, publishes a headline forecast each time. Beneath it sit assumptions and risks that could change the picture. This article covers a selection of them.

On spending, areas without a protected budget could face a 2.6 per cent a year real-terms cut in the final three years of the forecast. Spending on those areas would have to be £11 billion higher in 2031-32 for it not to fall in real terms from 2028-29. The Government's commitment to raise defence spending to 3.5 per cent of GDP by 2035 would cost around £35 billion in 2026-27 terms, which the OBR describes as the extra spending on defence by 2035-36. If health and disability benefit caseloads kept rising at the post-pandemic rate, welfare spending could be around £25 billion higher by 2031-32.

The margin for error is small. The current budget is forecast to be in surplus in 2029-30 by £15 billion. Since the pandemic, the average revision to borrowing before new policy measures in the third year of a forecast has been £18 billion. Separately, the median three-year-ahead difference between forecast and outturn since 2010 has been £34 billion.

Debt interest is forecast to rise to £160 billion in 2031-32. An average of £184 billion of maturing gilts (government bonds) are refinanced each year, typically at higher interest rates than the debt they replaced. A 1 percentage point change in gilt yields and Bank Rate expectations could change borrowing by £16 billion in the medium term.

On tax, the Government plans to reverse the temporary five pence fuel duty cut on 1 July 2027 alongside an uprating of rates; if implemented, rates would rise from 52.95 pence per litre to 60.59 pence per litre. The reversal has already been delayed five times. The tax-to-GDP ratio is expected to pass its historical high of 37.2 per cent in 2027-28. HMRC's latest tax gap estimate is £59 billion, and small businesses have accounted for more than 60 per cent of it since 2021-22.

Elsewhere, the OBR expects 190,000 fewer cumulative net additions to the housing stock than it did in March, and UK Export Finance expects to issue £40 billion of additional guarantees evenly between 2027-28 and 2030-31, which the OBR says increases the public sector's exposure to geopolitical risk.

What changed

The text says that, compared with March, the OBR expects 190,000 fewer cumulative net additions to the housing stock over the forecast period.

What it means

Written by AI and checked by a second AI. Published under the responsibility of VERADIQ's human director. Lens: economist

In practice, these points show how much of the forecast depends on choices not yet made. The 2.6 per cent a year squeeze on unprotected spending is what the Government's current spending totals imply, not a decision. Spending on those areas would have to be £11 billion higher in 2031-32 to avoid a real-terms fall.

It matters because the £15 billion margin is small beside the OBR's own record. Since the pandemic, borrowing in the third year of a forecast has on average been revised by £18 billion before new policy measures, which is larger than the margin. Separately, the median three-year-ahead difference between forecast and outturn since 2010 has been £34 billion, more than twice the margin (34 divided by 15 is about 2.3). These are two different measures and should not be added together or treated as the same thing.

Worth watching are interest rates, since a 1 percentage point change in gilt yields and Bank Rate expectations across the forecast could change borrowing by £16 billion in the medium term, and whether the fuel duty rise is implemented after five delays.

Who is affected

• Public services funded from unprotected day-to-day departmental budgets
• Taxpayers and businesses, including small businesses, as the tax-to-GDP ratio rises
• Motorists and fuel buyers, if the fuel duty rise takes effect
• People receiving health and disability benefits, and the welfare budget
• Would-be homebuyers and the construction sector
• Exporters backed by UK Export Finance guarantees

Key dates

• 1 July 2027 — Planned date for reversing the temporary 5p fuel duty cut alongside an uprating of rates
• 2029-30 — Year in which the fiscal mandate is forecast to be met by a margin of £15 billion
• 2031-32 — Debt interest spending is forecast to reach £160 billion

What the document does not say

• Whether the reversal of the 5p fuel duty cut will in fact take place on 1 July 2027: the text says 'if implemented', after five delays.
• Which departments or services would absorb the squeeze on unprotected spending: the text gives the overall effect, not where it would fall.
• Whether welfare caseloads will rise at the post-pandemic rate: the text gives it as a possibility alongside slower growth, not as a forecast.
• How far gilt yields will move: the text gives the effect of a 1 percentage point change, not a prediction.

Plain-English glossary

OBR

The Office for Budget Responsibility, the independent body that forecasts the UK economy and public finances.

Unprotected spending

Day-to-day departmental spending not covered by a specific funding commitment such as the NHS, defence or schools.

Real terms

Adjusted for inflation, so that changes show what money can actually buy.

Fiscal mandate

The Government's rule that day-to-day spending should be covered by receipts by a set year.

Gilts

Bonds the UK Government sells to borrow money.

Gilt yield

The interest rate the Government pays on its bonds.

Tax gap

The difference between the tax that should in theory be paid and what is actually received.

Tax-to-GDP ratio

Total tax receipts as a share of the size of the economy.

UK Export Finance

The Government's export credit agency, which guarantees support for British exports.

How this was checked

Status

confirmed

Checked by

claude, codex (OpenAI family)

Method

quote check (whitespace-normalised), digit guard, adversarial review, independent second-family review (codex CONFIRMED on third round after real wording problems were fixed), compliance review

Limits

The document is about 200 pages. This digest covers selected points about risks and assumptions, not the whole report. Locators give the PDF page marker (printed page is the marker minus 3) and paragraph number where visible. Figures are as printed.

Approved for publication

28 Oct 2026, 19:43 GMT

Not tax, legal or investment advice.

Corrections

No corrections have been made to this story.