Well, if you mean [some people] get together and figure out what to do spend money on and call it "the budget." Yes, I guess so.
But I mean, my understanding is that there is un-allotted money the government is willing to spend, beyond whatever budget they approve. My understanding was that, in particular, the military budget increases dramatically under these mechanisms.
Also - Social Security should also be separate, really, it's a trust fund with a very specific money - if we turned Social Security off tomorrow, it isn't like the money collected could go elsewhere. Money collected into that fund & being spent into that fund should not be able to be reallocated elsewhere.