If you have applied support packs or upgraded to ECC6 - then you may have encountered the effects of [Note 1311357|https://service.sap.com/sap/support/notes/1311357] - which prevented the ability to process returns against payments accepted in cash desk after the desk is closed.
Modification note 1604501
new note 1631779 (see below) has been created to remove that restriction.
This is a
modification, and will not be provided in standard. You must contact SAP in order to utilize it and to be made aware of the repercussions - cash desk balancing issues, etc.
Edited by: William Eastman on Jan 4, 2012 10:47 PM