When a credit memo is posted as shipped, you can see it in the Posted Return Shipment window.
The purchase credit memo was created when you clicked the Posting button on a purchase credit memo and then chose Post.
A purchase credit memo consists of a purchase credit memo header and one or more purchase credit memo lines.
The purchase credit memo header contains all the relevant information about the buy-from and pay-to vendors such as name, address, document number, and date. The program copied the information from the purchase header when it was posted.
The purchase credit memo lines contain information (such as item number, quantity and cost) copied from the posted purchase line.
You cannot change any of the fields on the purchase credit memo header because the credit memo has already been posted.