Field help (SIVTYP3) 

This information is used to determine the invoice type used to generate the sales invoice.
The invoice type identifies an invoice category (invoice, credit memo etc.) along with an entry structure for the validation of the invoices.
This field is initialized with parameter TYPINVFAS - Fixed Assets invoice type (chapter TRS, group INV) and can be modified. Only an invoice type with a legislation and company group consistent with those of the asset company can be entered.