Hello Daisy,
Please have a look at the chapter in HansaManuals regarding credit notes and stock:
http://www.hansamanuals.com/main/english/mailnumber___3362/theconf___515/manuals/levelzero___3358/version___71/hwconvindex.htm
If you have further questions after that feel free to ask them here.
Kind regards,
Edwin
HansaWorld Support