As a tool for organization, EMDECS inventory purchases can rely on purchase orders (POs) to receive against. This allows for reviewing price discrepancies and following backorders. Receiving against POs would be considered a best practice for most busy shops.
It is possible, however, to receive inventory without a PO. In EMDECS this is called Quick Receiving. Items received this way will adjust inventory levels accordingly in the system and the transaction can be invoiced in EMDECS if necessary.