[Koha] Where to store the invoice number against an item?

Hi all, If the Acq module is not being used by a library, where would be the best place to capture the invoice number for a specific item? I believe LOC recommends local field 923 $n for invoice number. http://www.loc.gov/marc/marc21-rda-vendors.html#local-fields What do you suggest? thanks -- Indranil Das Gupta Phone : +91-98300-20971 Blog : http://indradg.randomink.org/blog IRC : indradg on irc://irc.freenode.net Twitter : indradg -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-==-=-=-=-=-=-=-=-=- Please exchange editable Office documents only in ODF Format. No other format is acceptable. Support Open Standards. For a free editor supporting ODF, please visit LibreOffice - http://www.documentfoundation.org