well, I would actually suggest you to read a dedicated Section 6.3 Processing Payments in SAP treasury and Risk management (SAP Treasury and Risk Management (2nd Edition) - SAP PRESS Bookstore) if you have an opportunity, as it explains this process in details.
in brief, the process of payment processing could be structured like this:
- you post the respective flows from within the Transaction Manager (Transaction TBB1). Depending on if you are using payment requests functionality or not, the Credit side of your outgoing flow accounting entry should be either posted to so called 'Clearing account for Payment Requests' (you check your setup on IMG -> ... -> TRM -> Transaction Manager -> General Settings -> Payment Management -> Payment Requests -> Define Clearing Account for Payment Requests) or to so called Bank subaccount (you check your setup on IMG -> ... -> TRM -> Transaction Manager -> General Settings -> Payment Management -> Payment Handling -> Bank Account Transfers -> Define Account Determination) - both of these - the Clearing account for Payment Requests and a Bank sub-account - they are kind of Open items and in principle are intermediary accounts, used in the payment process - separate from an G/L account, representing the actual Bank account;
- this step is relevant only if you use payment requests functionality - then you call one of payment programs (F110 or F111). The payment program combines payments in the best possible way according to your setup and as a result accounting wise, it create a posting that debits the account that was previously credited (the Clearing account for Payment Requests) and, in turn, credits a Bank sub-account;
- the last step - bank statement processing. It represents the confirmation of the actual payment. However, the bank statement is not automatically fed back into the Transaction Manager. If a payment differs from what you expected at the time of posting, you must correct the business transaction. Accounting wise, when the bank statement is posted, in the selected case, the Bank sub-account is debited, while the actual Bank account is credited.
that kind of approach (vs Direct posting into Bank G/L account) is used for the simple purpose - it allows you to guarantee, that the balance your G/L, representing Bank account, in your books will always match actual figures in the Bank statement.
hope this will help you.
Kind regards,
Renatas