Under long-held constitutional practice, the Crown is charged with management of all revenue of the State and for all payments for public services. Therefore, the Crown is required to present their requirements for the financing of public services to the House of Commons on an annual basis.

This process ensures that government receives parliamentary consent before spending public money. All individual departments are therefore required to create Estimates, detailing their annual spending need for the forthcoming financial year.

As such, individual Estimates are scrutinised by departmental select committees, with specific questioning of officials surrounding certain aspects of the Estimate. The committee will form their conclusions regarding the Estimate, prior to further debate in the House of Commons.

The House of Commons will hold ‘Estimates Day Debates,’ which will typically enable debate for one or two departmental Estimates following scrutiny by departmental select committees. The House is invited to subsequently agree or reject the sums set out within the Estimates. All members of the House can table amendments to reduce the amount of resources or cash being spent prior to approval, but they are not able to propose an increase.

Estimates must also be reviewed and approved by HM Treasury (HMT) prior to being presented to parliament, where HMT will ensure that the estimate is consistent with budgetary controls as set out within Managing Public Money.

HMT will then present Estimates to parliament in a single publication, with the exception of some independent entities such as the National Audit Office, who present their own estimate.

Individual departments are therefore responsible for ensuring Estimates are consistent with their best forecasts of spending requirements and ensuring that they are consistent with HMT and parliamentary requirements.

There are various stages in the cycle for approving Estimates for one financial year:

1. Votes on Account
   The first step in the Estimates process, a Vote on Account is typically presented to parliament in January or February prior to the start of the financial year in April. This provides a provision for departmental spending for the early months of the financial year, prior to the Main Estimate being presented and approved in July.
2. Main Estimates
   Main Estimates set out each department’s proposed annual spending for the financial year and are usually published in April, prior to being approved by Parliament in July. They should present each department’s best forecast as to their income and expenditure for the financial year.
3. Supplementary Estimates
   Supplementary Estimates are usually presented in the final quarter of the financial year and allow for departments to revise their spending plans, perhaps because of a need to seek additional spending provisions, to reallocate funding between budgets, to recognise and add new areas of expenditure or income, or to reduce the spending provision where funding is not deemed required.
4. Approval of Estimates
   Once Estimates are approved by parliament, legislation is laid via the Supply and Appropriation Act which provides the necessary statutory authority for the total amount of resources, cash and capital sought within the Estimates for each department.

Two separate pieces of legislation are usually laid each financial year:

• The Supply and Appropriation (Main Estimates) Act, which follows approval of the Main Estimates. 
• The Supply and Appropriation (Anticipation & Adjustments) Act, which follows approval of the Supplementary Estimates and the Vote on Account.

Each piece of legislation sets out, for each department, their limits on departmental spending in line with budgetary controls (eg, RDEL, CDEL, RAME, CAME – see Public sector explainers: Public Sector Budgeting Framework), the limit on non-budgetary expenditure and the Net Cash Requirement for each department. Please see below an example of how the Estimates are set out in legislation:

Further Resources

• The Supply and Appropriation (Main Estimates) Act 2024 
• The Supply and Appropriation (Anticipation and Adjustments) Act 2024
• Supply Estimates: A Guidance Manual