Enter a customer for special stock &

What causes this issue?

You did not enter a customer for the customer-related special
stock &V1&.
You have to specifiy a customer for the following special stocks:
B,,material (to be) provided by the customer
V,,returnable packaging at customer's site
W,,consignment stock at customer's site

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Enter a customer number.

Error message extract from SAP system. Copyright SAP SE.