A red leather ministerial dispatch box on stone government steps, beside a chart of the 30-year gilt yield rising to 5.82%

The Savvy Investor's Guide

Gilt yields and the 28 October Budget: how the Chancellor’s fiscal headroom shrank

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James Heppe-Smith

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By James Heppe-Smith · 28 September 2026 · 9 min read

Educational, not advice. This article explains what has happened to UK government borrowing costs and public finances ahead of the Budget, and how that reaches household money. It is general information, not personal financial advice, and Savvy Investor Guide is not authorised or regulated by the Financial Conduct Authority. Nothing here tells you whether to fix a mortgage, buy an annuity, buy gilts or move your savings.

What this article covers: gilt yields in September 2026, what fiscal headroom is and which rule it is measured against, the published estimates of how much has gone, the August borrowing figures, and what higher yields mean for mortgages, annuities, savings and direct gilt buyers.

What it does not cover: what the Budget will contain, which nobody outside the Treasury knows before 28 October, or what any individual should do. United Kingdom only.

In short

  • On 8 September the UK sold £4.25 billion of 30-year gilts at a yield of 5.8168%. The figure is the Debt Management Office’s; Reuters reported it as the highest since comparable records began in 1998.
  • Fiscal headroom is the margin by which the government is forecast to meet its main fiscal rule. The last official figure, from the Office for Budget Responsibility in November 2025, was £22 billion.
  • Higher borrowing costs have eaten into it. On 1 September Capital Economics estimated the rise had cut the headroom by around £9 billion, to around £15 billion.
  • Borrowing is also running over forecast: £77.3 billion in the financial year to August, £8.1 billion more than the OBR expected.
  • The same yields reach households. Fixed mortgage rates have risen, annuity rates are high, fixed savings bonds pay above 5%, and gilt buyers can lock in yields not seen for decades.
  • The next official word comes on 28 October, when the Budget and the OBR’s forecast are published together.

Every Budget is built around a number most people never hear of until it goes wrong: fiscal headroom, the gap between where government borrowing is forecast to land and the limit the fiscal rules allow. In September 2026 two things squeezed that gap at once. The cost of government borrowing rose to levels not seen in decades, and the borrowing itself ran ahead of forecast.

This article sets out where each number comes from and what it means for the parts of your finances priced off gilts, without guessing at what the Chancellor, John Healey, will announce on 28 October.

What happened to gilt yields in September 2026

A gilt is a loan to the UK government. The yield is the annual return a buyer locks in at today’s price, which makes it, in effect, what the government pays to borrow for that term. When yields rise, new government borrowing costs more.

Yields jumped at the start of September. Hargreaves Lansdown, writing on 4 September, said 10-year gilt yields had topped 5.2%, “the highest level since the global financial crisis”, and that 30-year yields had hit highs not seen since the late 1990s.

The clearest single number came four days later. On 8 September the Debt Management Office, which borrows on the government’s behalf, sold £4.25 billion of a gilt that matures in 2056. Its result notice gives the price as £93.806 per £100, “equating to a gross redemption yield of 5.8168%”. Reuters reported that as the highest yield at a sale of this kind since comparable records began in 1998, and said investors placed £87.2 billion of orders. Unlike a market quote, which can move by the afternoon, that is a price actually paid, and the government will pay it on that gilt until 2056.

The pressure came from abroad as well. On 23 September the US 10-year Treasury yield rose from 4.96% to 5.11%, according to the US Treasury’s own daily data, its highest level since 2007. CNBC reported the next day that this came “amid a global government bond selloff” in which UK gilts also moved higher. On 24 September market data from Trading Economics put the UK 10-year yield at about 5.33% and the 30-year at about 5.82%.

For the longer story of how gilt yields feed through to mortgages and savings, see why UK gilt yields matter for your mortgage, savings and ISA decisions.

What fiscal headroom is, and which rule it is measured against

The government’s fiscal rules are written into the Charter for Budget Responsibility. Headroom is usually measured against the fiscal mandate, which the Office for Budget Responsibility summarises as “to have the current budget in surplus in 2029-30”. The current budget is day-to-day spending set against revenue, leaving out investment.

Headroom is how far inside that rule the forecast lands. In its November 2025 forecast the OBR said the mandate “is met by a margin of £22 billion (0.6 per cent of GDP)”. That is the last official figure.

There has been no newer one, and that is by design. The OBR’s March 2026 forecast says the government decided the OBR should assess the fiscal rules once a year, at Budgets, so that forecast “does not include an assessment of performance against the fiscal rules”. Every headroom figure you read between then and 28 October is an outside estimate.

How much headroom has gone: the estimates

Higher gilt yields cut headroom because they raise the interest the government expects to pay on its debt over the forecast period, and interest is part of the current budget. The published estimates date from the first days of September, when yields jumped.

Ruth Gregory of Capital Economics, quoted by the Telegraph on 1 September, estimated that the rise in borrowing costs had “reduced the Government’s Budget headroom by around £9bn, taking it from nearly £24bn at the time of the Spring Statement in March to around £15bn today”. She added that restoring it might take something like £9 billion to £14 billion of spending cuts or tax rises. The same day Bloomberg reported that the surge in borrowing costs had halved the government’s fiscal headroom.

Two cautions when reading those side by side. The starting points differ: Capital Economics begins from nearly £24 billion in the spring, itself an estimate, while the OBR’s last official margin was £22 billion in November 2025. And both are snapshots taken when yields were near their peak in early September; yields have moved since. The figure that settles it is the one the OBR publishes with the Budget.

The second squeeze: borrowing is running over forecast

Headroom also shrinks when the government borrows more than the OBR forecast, as it has been doing. The Office for National Statistics published the August 2026 figures on 22 September.

MeasureFigureAgainst the OBR forecast
Borrowing in August 2026£18.3 billion£3.5 billion above
Borrowing, financial year to August£77.3 billion£8.1 billion above
Public sector net debt, end of August93.8% of GDP0.8 percentage points below

Source: ONS, Public sector finances, UK: August 2026. The ONS called August’s figure the second-highest August on record, behind 2020, before adjusting for inflation.

The overrun is growing. The financial year to August was £8.1 billion above forecast, having been £2.3 billion above at the end of July. The debt ratio is the exception, coming in slightly below the OBR’s forecast at 93.8% of GDP.

What higher gilt yields mean for your money

Mortgages

Fixed mortgage rates are priced off swap rates, which move with gilt yields, rather than off Bank Rate, which the Bank of England held at 3.75% on 17 September. Lenders began raising fixed rates on 4 September and were still raising them in mid-September. The lender-by-lender record, with dates and sizes, is in the September 2026 mortgage repricing, and the mechanism is explained in UK mortgage rates turned back up in September 2026.

Annuities

Annuity rates are closely tied to gilt yields, so higher yields tend to mean higher annuity income. Which?, updating its annuity guide on 21 September, said rates for a healthy 65-year-old with £100,000 “have been above 7% since 2022 and consistently in excess of 7.5% since the start of 2025, even nudging above 8% recently”. For how annuities compare with other ways of taking a pension, see annuities in 2026.

Savings

Fixed-rate savings bonds tend to move with the same longer-term market rates. Moneyfacts reported on 17 September that the top fixed bond rates had “risen across the board this week”, with the leading five-year bond at 5.25% AER and every term offering at least 5.01%. Best-buy rates change weekly, so treat those as a snapshot.

Buying gilts directly

Someone who buys a gilt and holds it to maturity locks in the yield at the price they paid. Hargreaves Lansdown points out that “gains on gilts held directly are exempt from capital gains tax”, and says some investors prefer low-coupon gilts, where more of the return comes as a gain, to make the most of that exemption. It also warns that they tend to be higher risk if you need to sell before maturity, because their prices move more when yields change. Retail buying rose with the yields: Bloomberg reported on 3 September that gilt purchases on Freetrade’s bond platform had surged to their highest level of the year. How gilt prices are now reported to investors is covered in the UK bond consolidated tape.

What to watch before 28 October

  • Wednesday 21 October: September inflation figures from the ONS.
  • Wednesday 28 October: the Budget. The OBR has confirmed it will publish its Economic and fiscal outlook the same day, with the first official headroom figure since November 2025.
  • Thursday 5 November: the next Bank of England interest rate decision.
  • Gilt yields in between: every move in the weeks before the Budget changes the interest cost the OBR builds into its forecast.

Common questions

What does fiscal headroom actually mean?

It is the margin between the government’s forecast borrowing and the limit set by its own fiscal rules. A larger margin gives the Chancellor room to absorb bad news without changing policy. A smaller one means higher interest costs or weaker tax receipts can push the forecast towards breaking the rule.

Why do gilt yields affect the Budget?

The government borrows by selling gilts, so the yield is its borrowing cost. When yields rise, the interest it expects to pay over the forecast rises too, and interest counts against the current budget that the main fiscal rule measures.

Does this mean taxes will rise in the Budget?

Nobody outside the Treasury knows what the Budget contains. Outside forecasters expect the headroom to be smaller than it was, and Capital Economics put the gap to restore it at around £9 billion to £14 billion, from spending, taxes or both. The Chancellor could also choose to run with a smaller margin. The decision is announced on 28 October.

Is a 30-year gilt yield of 5.8% a record?

The 5.8168% at the 8 September sale was reported by Reuters as the highest at a sale of its kind since comparable records began in 1998. That is a record within the modern series, not across the whole history of government borrowing: yields were far higher in the 1970s and 1980s.

If I bought gilts, would I lose money if yields rose further?

If you hold a gilt to maturity, you receive the payments and the face value that were set when it was issued, whatever happens to yields in between. If you sell before maturity, the price you get depends on yields at that moment, and when yields rise, prices of existing gilts fall. Longer-dated gilts move the most.

Sources

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