Enter a valid reversal reason

What causes this issue?

There reversal reason you have entered is not valid. There are two
possible reasons:
It does not exist (that is, it has not been defined in Customizing).
This reversal reason does not allow you to enter a different posting
date in the reversal document from the one contained in the original
document.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.