How to check and release vendor payment in SAP How to lock invoices in SAP regarding vendors/Accounts Payables How to lock time period in SAP?

You can either directly go to the document number via FBV0 and view the double entry or you can go t vendor line item display FBL1N and and check for duplicate reference/amount/date/ etc.  and FBL3N for the bank out verification

You can go to FBL1N- Vendor Display and view for all the open/cleared/reversed/parked invoices as required. 

You can view it using the Tcode FKN - Display Balances. you can even double click it and view the individual breakup as well. 

Note: Please note that i have answer only the basic guidance. Please revert if you require detailed procedure and guidance.