Formula error: Identifier expected instead of &1

What causes this issue?

The formula syntax is incorrect. An identifier or a key figure is
expected instead of the formula element displayed.

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?

Correct the formula.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.