Error "Special G/L transactions of type A are not supported" appears when using the Fiori Apps, such as "Clear Incoming Payments", "Clear Outgoing Payments", "Post Incoming Payments" and "Post Outgoing Payments".
SAP S/4HANA CLOUD
It is not supported to manually enter or post on account with a Special G/L indicator of type A.
In the Fiori Apps, special G/L transactions of type A can be used only in combination with a down payment request.
With regard to down payments, you can kindly refer to best practices:
Accounts Payable (J60): https://rapid.sap.com/bp/scopeitems/J60
Accounts Receivable (J59): https://rapid.sap.com/bp/scopeitems/J59
Special G/L account, Special G/L indicator, Clear Incoming Payments, Clear Outgoing Payments, Post Incoming Payments, Post Outgoing Payments, F5246, Special G/L transactions of type A, Down payment request , KBA , FI-FIO-AR , Fiori UI for Accounts Receivable , FI-FIO-AP , Fiori UI for Accounts Payable , Problem