If you're on an agile team, every two weeks there is a thing called a retrospective. At the end of two weeks, we have a little Lego block of value that we deliver and the team gets together and asks if they delivered the value they thought they were going to deliver. The answer is yes or no, and then they ask if they can do anything better on the next iteration to deliver a bit more. They have that discussion and then they go for another two weeks.
At the end of the quarter, we have a bigger retrospective, at maybe a more senior level, that asks, “Did we deliver the value and the outcomes that you were looking for? If not, why not? How are we doing on budget?”
The other thing I'll say about budget is that it's extremely predictable. I know that I have a team of five or six people running this. I know that this three months and the next three months will be probably within 10%. I get very predictable flow rates of budget allocation.