FM Budget check on basis of Payment Terms in Vendor Master

Dear Experts,

In our scenario, Payment terms are defined & assigned as 45 days in Vendor Master. Posting date is included in Source fields of derivation rules so budget is subject to periodic basis.

Practically system is checking and consuming FM budget, in FB60, on the basis of Payment terms as assigned in Vendor Master which should not happen. For example, a Vendor Invoice is posted in FB60 on 01-Jun-2021 whose payment terms allow him 45 days. At time of saving the document, the system checks & consumes budget of July 2021 (which is wrong). Now if I change payment terms as 15 days or 30 days for same kind of invoice (posting date same 01-Jun-2021), then system checks & consumes budget of June 2021.

Our requirement is to check & consume budget in the period of posting date in FB60 irrespective of payment terms duration.

Please advise the appropriate solution.