They do. Major policy announcements made in the budget will include expenditure to implement those policy announcements if the planning has proceeded far enough to enable that to be done. If it hasn't, the announcement might be made in the budget but a supplementary estimate will be presented to the Parliament later in the financial year to give the financial authority for what has been announced in the budget. It's a combination of the two, really.
On April 4th, 2012. See this statement in context.