Supplying and receiving plants identical (Please check)

What causes this issue?

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

System Response

How to fix this error?

In the field "Plant" you enter the key of the plant that is to receive
the goods.
In the field "Supplying plant" you enter the key of the plant from
which the goods were issued.

Error message extract from SAP system. Copyright SAP SE.