FusionRetail 6 provides you an easy to setup security system so that you can provide the appropriate rights to the user.
Modifying or deleting a back dated transactions is purely a company policy. It may differ from organization to organization.
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Q: If I have no rights for deletion or modification then how can I solve wrongly enter voucher in a particular date range?
A: In any case modification and deletion is to be done by the person who is authorized to do so.