What is kbs transaction key in sap?

KBS transaction key is used for account determination of Account assigned PO's and. In Standard SAP, for transaction event key KBS, account determination is not active. You do not have to define these transaction keys, they are determined. seen at Accounting Journals of SAP Material Management (MM) Transactions. KBS – is without any account determination and posting keys are 81 & 91. PS : when I manually fill in the GL account and post via MIRO the invoice, the Accounting document is created with KBS Transaction, so I.