Ask HN: Do you need to have your budget allocated to raise money?

This is kind of a simple question, but if we are raising more money than we can allocate until our next milestone, will that be a problem in raising this amount? Do investors expect all of your raise to be allocated into specific budgets you're committed to? Or can it be flexible as the business evolves?

How well did you have to specify your budget in advance, when you raised?