In countries using the Westminster system the Estimates are a series of legislative proposals to parliament outlining how the government will spend its money.
The Estimates are drawn up by bureaucrats in the treasury department in collaboration with representatives from the cabinet. They consist of detailed reports on how each department or ministry will spend its money. The estimates are normally introduced in the House of Commons just prior to the main budget, which gives them time to be analyzed by House committees. Unlike the budget the estimates contain no references to fiscal policy, long term goals, or where the money is coming from. After each section is reviewed by the relevant committee the entire Estimates are voted on as one bill. This "supply" vote is a matter of confidence. Unlike tax proposals in the budget, the Estimates are rarely controversial, with most issues being dealt with in committee.
Most of the countries also mandate an update or series of updates to the Estimates to account for changes in the economy or in government policy. In Canada, for instance, this update must be passed in December each year.
McMenemy, John. "Estimates' The Language of Canadian Politics. 1995