Reply required - cannot be deleted

What causes this issue?

You tried to delete a document with the attribute <ZK>Reply required
</>. You have to reply to the document before you can delete it.

System Response

How to fix this error?

Reply to the document with <LS>Document -> Reply</> or <LS>Reply
w/reference</> and then delete it.

Error message extract from SAP system. Copyright SAP SE.