Deactivation date & later than today's date (Correct)

What causes this issue?

The deactivation date you have entered is later than today's date. The
system only allows you to deactivate up to and including the current
date. You cannot postdate.

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?

Error message extract from SAP system. Copyright SAP SE.