This email is in reference to the request regarding _______ (leave/work error/misconduct) excuse. This is to inform you that it has been ____ (days) since, we have requested you to submit the excuse for the same. As you know that we need this document for maintaining the official records.
We did not expect this delay from your end and please consider this email as your last warning. If you fail to submit the required documents, we will have to take necessary action against you without any prior intimation.
___________ (Contact Details)