ap_checks_all.payment_type_flag

Oracle Payables application uses bank_account_num, bank_num, and bank_account_type for the supplier's bank information when you use the electronic payment method.

Also, payment_type_flag code M and Q which designates payments created by recording a manual payment or quick payment, respectively will populate the bank_account_num column.  
But a payment_type_flag of A which designates payments created by the payment batch process will not populate the bank_account_num column.