Constitutions specify the role of the legislature and its relationship with the executive. Constitutions and/or budget system laws elaborate on the budgetary roles and powers of the legislature. Parliament’s main roles are to review and debate the government’s draft ex ante budget (including its revenue estimates and its spending plans) and to authorize spending to implement the annual budget plan. The budget is the most important economic policy tool of a government and provides a comprehensive statement of the priorities of a nation. As the representative institutions of the people, national legislatures are the appropriate place to ensure that the budget optimally matches a nation’s needs with available resources. Effective legislative participation in the budget process establishes checks and balances that are crucial for transparent and accountable government and ensuring efficient delivery of public services.