Depreciation key & not allowed (Check your entry)

What causes this issue?

Depreciation key &V1& is not defined.

System Response

Processing is terminated.

How to fix this error?

You have the following choices:
Use a defined depreciation key (use input help).
Define a depreciation key in Customizing ("change" pushbutton) and
activate the key.

Error message extract from SAP system. Copyright SAP SE.