Is it possible to disable the budgetary control for the account being used

Hi Experts ,

Customer using top down budget in project (Gl integrated budget ), customer defined the budgetary control and defined the budget in project and  attached one account from GL.

Also customer created the Purchasing and payable invoice using the same account and project fund check.

Now the concern is , is it possible to disable the budgetary control for the account which is being used in PO/AP,

1 If yes ,what the the impact of  existing PO/invoice which is already created using the same account

2 what about the  available budget amount for that account

provide the detailed steps for the same