In an unprecedented and highly disruptive turn of events, the Office for Budget Responsibility (OBR) accidentally published its full Economic and Fiscal Outlook nearly an hour before Chancellor Rachel Reeves was due to present the UK Budget 2025.
The premature release — live for a short period on an unprotected link — exposed major tax increases, extended freezes to income tax thresholds, sweeping changes to pension contributions, and new levies on property and electric vehicles.
The leak triggered instant volatility in UK markets, political backlash in the Commons, and a formal investigation from the OBR as its revelations reshaped expectations ahead of the Budget speech.
Key Takeaways: UK Budget 2025 Revealed Early After OBR Technical Error
- OBR accidentally publishes a full Budget forecast before Reeves’ speech.
- Major tax changes amounting to £26bn planned by 2029–30.
- Income tax thresholds are frozen until 2030–31, pushing more people into taxation.
- Fiscal headroom rises to £22bn — £12bn higher than March forecast.
- New mileage tax for electric vehicles from 2028.
- NICs charged on salary-sacrifice pension contributions, raising £4.7bn.
- Council tax surcharge planned for properties over £2m.
- GDP growth downgraded compared to March OBR outlook.
- Markets move sharply as gilts rally then reverse.
- OBR launches investigation after calling it an unprecedented leak.
OBR’s Premature Publication: A Leak Without Modern Precedent
The government’s financial watchdog unintentionally uploaded its completed Budget response on Wednesday morning, nearly 45 minutes before Rachel Reeves was scheduled to address Parliament. The link, which remained public briefly, allowed full access to all economic projections, fiscal assessments and policy impacts.
The document was first identified by Reuters before being widely circulated. Within minutes, gilts surged as traders responded to unexpected fiscal clarity, though the rally was short-lived. The pound also touched session highs before settling.
Conservative leader Kemi Badenoch condemned the release as an unprecedented failure, calling it “an unprecedented leak” and criticising Labour’s fiscal direction.
OBR Issues Apology and Confirms Internal Investigation
Shortly after the document was taken offline, the OBR issued a formal apology, calling the incident a “technical error.” It confirmed a full investigation and committed to report its findings to:
- The OBR Oversight Board
- The Treasury
- The Commons Treasury Committee
The watchdog promised stronger safeguards to prevent future breaches, emphasising that its official documents would be republished only after the Chancellor concluded her Budget speech.
Fiscal Outlook: Headroom Rises but OBR Warns It Remains Fragile
The leaked forecast shows Reeves’ Budget will increase fiscal headroom to £22bn, a jump of £12bn compared to the OBR’s March projections. This expanded buffer is intended to reassure investors of the government’s ability to manage unexpected shocks.
Also Read: UK Autumn Budget 2025: Tax Rises, Cost-of-Living Crisis and Industry Pushback
However, the OBR stressed that the headroom remains “small” given the scale of economic uncertainties and the complexity of the new tax measures.
Growth Forecasts: A Mixed Economic Picture
The OBR’s leak reveals:
| Year | Previous Forecast | Updated Forecast | Notes |
| 2026 | 1.9% | 1.4% | Significant downgrade |
| 2025 | 1.0% | 1.5% | Upgraded due to stronger early-year performance |
While the near-term outlook improved, medium-term growth faces downward pressure due to weaker productivity and rising household tax burdens.
Major Tax Changes: £26bn in New Measures by 2029–30
The leak outlines a wide range of new and extended tax measures:
1. Income Tax Threshold Freeze Until 2030–31
One of the largest contributors to revenue growth.
Frozen thresholds:
- Personal Allowance: £12,570
- Higher-Rate Threshold: £50,270
- Additional-Rate Threshold: £125,140
The freeze is expected to pull millions more into higher tax brackets and generate £8.3bn.
2. NICs on Salary-Sacrifice Pension Contributions
A major structural change:
- NICs exemption capped at £2,000
- Expected revenue: £4.7bn (2029–30) and £2.6bn (2030–31)
Industry bodies warn this will reduce take-home pay and discourage long-term pension savings.
3. 2% Increase in Tax on Savings, Dividends & Property Income
The OBR lists this as one of the Budget’s unexpected elements, expected to significantly increase annual revenues.
4. Council Tax Surcharge on High-Value Properties
Properties valued over £2 million will face additional council tax charges, raising approximately £400m in 2029–30.
5. Mileage-Based Charge for EVs and Plug-In Hybrids (2028)
A landmark policy shift:
- Introduced April 2028
- Expected to raise £1.4bn
This marks one of the UK’s first large-scale taxation measures specifically targeting electric vehicles.
6. Removal of Two-Child Limit in Universal Credit (April 2026)
A major welfare reform reversing previous policy and expanding support for larger families.
7. Additional Revenue Measures
- Reduced capital gains relief on Employee Ownership Trusts: £0.9bn
- Tax administration, compliance and debt collection improvements: £2.3bn
- Sizewell C RAB levy and related measures: £4.4bn
- Fuel duty freeze for five months, with staged increases from 2026
Political and Public Reaction: Heated Exchanges in Parliament
During Prime Minister’s Questions, Sir Keir Starmer described the upcoming Budget as rooted in “Labour values,” promising support for families struggling with cost-of-living pressures. He emphasised commitments such as free childcare, free school meals and NHS waiting list reductions.
Opposition figures, meanwhile, argued the leak demonstrated poor fiscal management and warned that the extensive tax rises would deepen the burden on working households and pensioners.
Market Response: Volatility Reflects Sensitivity to Fiscal Surprises
The leaked document triggered an immediate rally in government bonds, with 10-year gilt yields falling before rebounding and ending the session slightly higher at 4.535%. The movements reinforced how closely financial markets are tracking fiscal discipline and borrowing costs.
What This Early Leak Means for Britain’s Economic Path Ahead
The premature publication of the OBR’s Budget analysis has laid bare a fiscal strategy built heavily on tax rises, frozen thresholds and revenue-driven reforms. With £26bn in new measures, frozen allowances until 2030–31, and a downgraded medium-term growth outlook, the UK enters a period of tightened household finances and careful economic balancing.
The expanded £22bn headroom offers some reassurance, but the OBR’s warnings underline the fragility of the outlook and the importance of execution in the months ahead.
FAQs on the OBR’s Accidental UK Budget 2025 Leak
1. What was leaked by the OBR before the UK Budget 2025?
The OBR accidentally published its full Economic and Fiscal Outlook, revealing tax changes, growth forecasts, frozen thresholds and major policy measures before Rachel Reeves’ speech.
2. Why did the OBR leak cause market volatility?
The early release gave traders unexpected fiscal clarity, triggering a brief gilt rally, yield swings and a short-lived jump in the pound.
3. What major tax changes were revealed in the OBR leak?
The leak exposed £26bn in tax rises, frozen income tax thresholds, NICs on salary-sacrifice pensions, EV mileage charges and higher taxes on savings and property income.
4. How much fiscal headroom will the government have according to the leaked forecast?
The OBR leak shows fiscal headroom increasing to £22bn, which is £12bn more than projected in March.
5. What new policies affecting households were confirmed in the leak?
The leak confirmed the freeze on tax thresholds, removal of the two-child limit in Universal Credit, new EV charges and a council tax surcharge on £2m-plus properties.
