Well,
Handbook 2, 13.2.8 says that "Expenditures must be approved by the stake presidency or bishopric before they are incurred." There are a few varying opinions on what that means. Some think that that means that the bishopric has to approve every purchase before the money is actually spent. Others view this as part of the bishop's oversight of the budget, and say the bishop[ric] can simply approve the incurring of expenses for an approved activity as part of an organization's approved budget. ["Yes, Ward council, go ahead and spend the $200 we have budgeted for that activity.") Ultimately, it's up to the bishop, and the ones he counsels with, to determine the best use of the bishop's scarce time.