When you post documents in SAP, there are instances where the system also adds some more line items (such as tax, cash discount, gain/loss from foreign exchange transactions, etc.) besides the ones you have entered in the document. This helps to reduce your work as the system calculates these automatically. However, you need to define accounts you want the system to automatically post to; this will ensure that no manual posting is allowed to any of these accounts.
Great. Thanks really helped to understand.