Explanation
When creating an invoice with purchase order reference, unplanned delivery costs can occur if the invoice amount exceeds the order amount. These costs can be posted automatically by selecting one of two options in Customizing: distribute costs or post to separate account. If distribute costs is selected, the costs are distributed proportionally among the invoice items according to their net value. If post to separate account is selected, the costs are posted to a separate general ledger account that is determined by account determination. The other options are not available for automatic posting of unplanned delivery costs. References: [SAP Help Portal],
[SAP Community]