Field help (TYPVCR) 

This field enables the user to specify the type of the supplier invoice originating the expense. The default value is 1 - Invoice. If the type is: 2 - Credit Memo, the positive amounts will turn into negative amounts, and vice versa for the other types of invoices (except for the Invoice type, which can have a negative amount).
The amounts entered in the free text sections will be saved with the sign specified by the user.
Update 8.0.0 and higher:
When the expense has been generated automatically after a discount line creation, the invoice type is: Early discount/Late charge and cannot be modified.