Posting key in SAP is used to control the entry of a document line item. In SAP a posting key determines the account type, debit and credit of
Document types are used to distinguish between various accounting documents and controls the header information. While entering a document you enter the document type in the header section.
Posting key in SAP is specified or defaulted for each line item and it controls how the line item is entered and processed. These Posting keys in SAP