docs/STABLE/gncIDSearch_8h_source.html

 #include <config.h>
 #include <glib/gi18n.h>
 #include <regex.h>
 #include <glib.h>
 #include <glib/gstdio.h>
 #include "qof.h"
 //#include "gncAddressP.h"
 #include "gncCustomerP.h"
 //#include "gncCustomer.h"
 #include "gncInvoice.h"
 #include "gncBusiness.h"
 // query


 #ifndef GNC_invoice_import_invoice_import_H
 #define GNC_invoice_import_invoice_import_H


 GncCustomer * gnc_search_customer_on_id  (QofBook *book, const gchar *id);
 GncInvoice  * gnc_search_invoice_on_id   (QofBook *book, const gchar *id);
 GncInvoice  * gnc_search_bill_on_id   (QofBook *book, const gchar *id);
 GncVendor  * gnc_search_vendor_on_id   (QofBook *book, const gchar *id);

 #endif
gncBusiness.h
– Business Helper Functions

GncCustomer
credit, discount and shipaddr are unique to GncCustomer id, name, notes, terms, addr, currency, taxtable, taxtable_override taxincluded, active and jobs are identical to ::GncVendor.

gncInvoice.h
Business Invoice Interface.