What are Supply days in Parliament?

Supply days (also called Allotted Days or Opposition Days) are the 22 days each year in the House of Commons reserved for the Opposition to choose the topic of debate. Supply days are an outgrowth of the constitutional principle that the executive needs the consent of the elected House to obtain supply (the money for government operations). In exchange for approving supply, the Opposition gets time to debate topics of its choosing.

Supply days are distributed across three supply periods in the parliamentary calendar: 7 days in the supply period ending December 10, 7 days in the supply period ending March 26, and 8 days in the supply period ending June 23. Days are allocated among the Opposition parties according to their seat counts: in a typical Parliament, the Official Opposition gets about 14 to 16 days, with the remaining days distributed among the smaller Opposition parties. The Official Opposition House Leader and the smaller parties' House Leaders coordinate the schedule.

Each Supply day, the Opposition party allocated the day proposes a motion on a topic of its choosing. The topic can be policy criticism, demand for inquiry, non-confidence motion, or any other matter within federal jurisdiction. Debate on the motion takes the full day (about six hours of speaking time), and the motion is voted on at the end of the day. Recent Supply Day topics have included the Liberal government's handling of housing affordability, the carbon tax, foreign election interference, and the approval of the Trans Mountain pipeline expansion.

Supply days are also when the House of Commons votes on the Estimates, the formal authorisation of federal spending. The Main Estimates are typically voted on the last Supply day of each supply period, with departmental Estimates studied by the relevant standing committee in the weeks beforehand. The Estimates motion is technically a confidence matter, though the Opposition rarely tries to use it to trigger an election. Combined with the Throne Speech Address in Reply, the Budget vote, and major government bills, the Estimates votes are the principal confidence votes of the parliamentary year. If the government loses any of these votes (a rare event in modern Canadian history but common enough in minority parliaments), it must resign or call an election.