Field help (BPCINV)

It is the code for the bill-to customer, which is initialized by default with the customer code entered in the header.
This customer can be another customer chosen from the customer table.

It is possible to search a customer or several customer grouped under the same criteria by selecting 'Quick customer search'. A list of matching items is generated on tabulating to the next field.
For a more advanced search, all fields present in the block can be entered. The list of matches is narrowed down with each tabulation.