What is the best practice for the timing for closing the AP subledger?  Last day of the month?  T-1?  etc.  If an AP subledger does not exist, e.g. S4 Hana, what is the best practice for cutting off payments?

T-1 or T-2 to allow sufficient time for processing and resolving any outstanding transactions or discrepancies before finalizing the month-end financials, but that depends on the processes in place and that can change from company to company.   Even if an AP subledger does not exist, such as in SAP S/4HANA where the traditional subledger concept may not apply in the same way, the best practices for cutting off payments would still involve similar principles.

We close our AP Ledger on T-1 in order to ensure posting of accruals if any for revenue recognition process. Similar approach can be followed.