Alternate ID for a purchase receipt
On the screen or on the printed report?
I don't think one is there on the screen. But, let's say you have this setup in the Stock Items (IN202500) screen with an alternate vendor part number defined:
You can enter the vendor part number (eg. ACERLAP-2A) on the Purchase Receipts (PO302000) screen
And, as soon as you tab out of the field, it automatically converts it to the internal part number: