idoc failing to post GR due to date varience between po and confirmation

HI All

GR posting idoc is failing due to date varience between PO delivery date and confrimation delivery date. it seems somewhere in the configuration date varinece maintained as 0 days. so whenever po delivery date and confrimation date is not equl then Idoc failing to post GR. can any one please let me know the transaction code for this setting?