Solution : https://service.sap.com/sap/support/notes/494541 (SAP Service marketplace login required)
Key words :
system transfers customer enhancements analogously, enterprise buyer professional edition, exchange user-defined fields, customer include ci_bapi_###_c, user-defined fields, customer defined extensions, customer include ci_bbp_item_po, customer include ci_bapi_po_item_d, customer include ci_bapi_po_item_vd, customer include ci_bapi_inv_header_c-
Related Notes :
| 825169 | XML: Bid currency in bid invitation |
| 806127 | User-defined fields with XML communication |
| 659386 | PO output in case of customer field changes |
| 618400 | Support Package 01 for SRM 3.0 |
| 458591 | User-defined fields: Preparation and use |