From the Australian Parliament House website
Twice each year estimates of proposed annual expenditure of government departments and authorities are referred by the Senate to eight legislation committees for examination and report. These estimates are contained in the main appropriation bills introduced into Parliament as part of the budget (usually in May) and in the additional appropriation bills introduced later in the financial year (usually in February). A round of supplementary hearings is usually held in October.
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Visit the Australian Parliament House website here to see inquiries currently underway.