Budget Groups setup is optional !
Budget Groups provide sets of criteria to support a secondary budget control check in the event that the primary budget control check as defined by the criteria specified for budget control rules fail.
If there was a budget control rule for all combinations of the department and cost centre financial dimensions, you could also define a budget group for Department 010, which would include all the cost centres in that department. This budget group would pool the budget of all the cost centres for Department 010. If an initial budget check failed for a cost centre in Department 010, a second budget check would be performed on the aggregate budget for all cost centres in Department 010.
To perform the secondary budget check, the Overbudget option for budget group check setting in the User group budget permissions form for budget control rules must be set to Perform budget group check when budget funds are not available.
Further information on Dynamics 365 Basic Budgeting and Budget Control is available on the Microsoft Docs and Learn Docs sites via the URLs below and should help to provide further background and context to aid survey question completion.
Background and information on the Public Sector specific elements of Basic Budgeting and Budget Control are provided via the URLs below for reference purposes.