Both houses of Congress have their own budget committees. The job of the budget committee is to draft a budget resolution that sets the rules for the Appropriations Committee. (Of course, once the committee drafts the budget resolution, it still has to be approved by both houses, and can be amended on the floor of the house.)
The President's budget is merely the request of the President to those budget committees. However, the President's budget is not legislation and has no binding legal effect. The budget committees get to pay as much or as little attention to the President's proposed budget as they see fit. (And normally, they put it to the side very quickly and do what they want to do, not what the President has proposed. No President in the past 40 years has had their budget adopted anywhere near intact.)
I thinks It’s b.budget office
Hope that helps