SAP Note 12791 - Reversal of GR not possible after IR w. GR-b. IV

Symptom:

If you posted a goods receipt and the relevant invoice for an order
item with goods-receipt-based invoice verification, you can only
reverse this goods receipt (movement type 102) or send it back to the
vendor (movement type 122), if you have previously posted a credit
memo for the invoice.

Cause and prerequisites

In order to avoid the situation "quantity invoiced greater than
quantity of goods received," the system has been designed so that a
goods receipt can only be reversed after the invoice has been
cancelled.

Solution
As of Release 3.0, SAP enables posting of return deliveries even without
prior cancellation of the invoice. If you wish to utilize
this functionality, you have to activate it the Customizing system (see
30A Release Information titled "Inventory Management: Goods Receipt
Reversal for GR-Based Invoice Verification"). Up to Release 3.0 (or if
you have not activated this function), a credit memo has to be posted
before the goods are returned.

Additional key words

M7021 OMBZ

Key word: GR-b. IV, GR rv