You must refer to a sales and distribution document, e.g. a delivery or a credit memo request.
You will reach the screen Create billing document.
There is the following prerequisite in Customizing for item selection during delivery-related billing.
Billing relevance of the item category must have the indicator K.
If errors occur, you can display the notes on these errors in the log (Edit® Log).
In this case you have no more influence on the billing documents.
As long as the sales and distribution documents were not incomplete or did not contain any errors, the number of the last billing documents created is displayed.
If errors occur during account assignment and you can not get rid of these, you must cancel the billing documents.