Estimates Day debate: Spending of the Ministry of Defence

On Wednesday 4 March 2026, there will be an Estimates Day debate on the spending of the Ministry of Defence. The topic for the debate was proposed by the Backbench Business Committee, on application from Tan Dhesi MP, Chair of the Defence Select Committee. Following the debate, the House will vote on whether to approve the Supplementary Estimate for the Ministry of Defence for the 2025/26 financial year.

What are the Estimates?

One of Parliament’s longest standing functions is the consideration and authorisation of the government’s spending plans. Estimates, sometimes known as Supply Estimates, are the documents presented to Parliament setting out the government’s plans for spending for a given year.

The process of obtaining Parliamentary approval to those plans is known as ‘supply’. With a few specific exceptions, the government is required to obtain authority from Parliament through the supply process before it can spend public money.

Content of an Estimate

Separate Estimates and Votes on Account are produced for each government department and published together by HM Treasury in a single volume. The key components of each Estimate are spending limits and ambits (what the money will be spent on). These apply to a single department for a single year only.

Spending limits

Within each Estimate, spending is divided into four categories determined by HM Treasury, each of which has its own budgetary limit. Changes to the categorisation of spending require prior consultation with Parliament.

The Treasury does not normally allow departments to move money from its capital budget to resource budget (although exceptions, such as for health, are sometimes made), or from AME to DEL. Once Parliament has voted the limits, savings on any voted limit (DEL or AME) cannot be used in support of spending under another.

Ambits

The ambit is the description of what the spending within each of the limits will be used for. Government departments must ensure that their ambits are accurate and, subsequently, that no spending falls outside their scope. Should it do so, it would constitute an ‘excess vote’: illegal spending outside the authority authorised by Parliament.

Detail of spending plans

Each Main and Supplementary Estimate contains further detail of spending plans, breaking the spending limits for each category above into a number of lines, known as subheads.

These breakdowns represent the government’s best estimation of planned spending within four categories at the time the Estimates are prepared. However, these subheads are not limits; government departments are free to switch resources from one subhead to another, providing they do not exceed the overall spending limits, or incur expenditure beyond the scope of the ambit.

Ministry of Defence Supplementary Estimate 2025/26

The Supplementary Estimates for the 2025/26 financial year were published by HM Treasury on 10 February 2026.The Ministry of Defence (MOD) provided its explanatory memorandum alongside the Treasury document, and this was published by the Defence Committee.

The Supplementary Estimate contains an increase to the MOD’s total managed expenditure (the total of both DEL and AME budgets) for 2025/26 of £16,233 million, or 22.4%. Following the uplift at the Supplementary Estimates, the Ministry of Defence would have total managed expenditure of £88,409 million for 2025/26.

The largest portion of this uplift (£9,000 million) is allocated to ‘depreciation or impairment’ and is due to the effect of a ‘non-routine accounting adjustment’. The MOD, in its memorandum, did not provide further information about the increased cost, such as whether it is for depreciation or an impairment. Depreciation is an accounting treatment which recognises the cost of the gradual deterioration of assets over time. Impairments are accounting adjustments to recognise the significant loss of value of an asset due to loss, damage or obsolescence.

The Supplementary Estimate also contains uplifts for operational support for the Coalition of the Willing in support of Ukraine, increases for research and development and significant increases for ‘provision costs’. Provisions are financial liabilities likely to incur costs to the MOD in the future. The MOD’s provisions cover the future costs for legal claims, civilian early departure costs, environmental costs, restructuring and nuclear decommissioning and restoration costs.

For more information about the 2025/26 Supplementary Estimates, see the Library briefing: Revised Government spending plans for 2025/26

For an interactive dashboard exploring departmental breakdowns, see the Library dashboard Supplementary Estimates data: Government spending plans for 2025/26