In order to make expenditures, the government must receive Parliament’s approval, either through previously adopted legislation or, on an annual basis, through the introduction and passage of appropriation bills. Prior to the introduction of each appropriation bill, the President of the Treasury Board tables an Estimates publication (Main or Supplementary) in Parliament to provide information and details on spending authorities sought.
While the Main Estimates provide an overview of spending requirements for the upcoming fiscal year, Supplementary Estimates present information on additional spending requirements which were either not sufficiently developed in time for inclusion in the Main Estimates, or have subsequently been refined to account for developments in particular programs and services.