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Purchase Return, on the other hand, is related to calculate amounts to be received by the buyer against goods returned to the Vendor due to quality and / or price issues.
Purchase Service Invoice (Adhoc) makes it possible to make payments for services to run the organization’s business, procured on the fly, without raising an order.
Purchase Service Invoice (against order) is raised for services which have been formally ordered and received.
Purchase Debit Note is raised, on buyer side, to handle the human errors done by vendors.
Purchase Credit Note is raised, on vendor side, to handle the human errors done by buyers.