How should the budget approval process be set up so it doesn't slow down procurement?

If the budget approval process relies solely on the boss's final signature, it will quickly become a bottleneck where all procurement requests are queued up waiting for one person. Small amounts get delayed, while large amounts lack business justification. Finance only discovers there's no PO, no budget category, or that the approver isn't the budget owner when they receive the invoice. I've impl…