Cross-company code transaction in contract item &1 &2, company code &3

What causes this issue?

You are entering an invoice for a contract that is assigned to another
company code.

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?

Check the document number you entered, and the company code in which you
are working. Correct your entry, as applicable.

Procedure for System Administrators

In Customizing, you can set this message as a warning message, an error
message, or an information message.

Error message extract from SAP system. Copyright SAP SE.