A written warning email will not only give employees the chance to correct their mistakes but is also evidence that notice was given to an employee before further actions are taken.
You can send an email like this following a meeting with the employee or prior to a meeting/escalation of the issue.
Email subject line: Warning notice for [Misconduct]
Dear [Employee Name],
We regret to inform you that we have been made aware of your [Misconduct] and would like to let you know that this is not what we expect from [Company’s] employees.
Please note, this is your first official warning and if repeated, we may take further action including termination of your employment with [Company].
We encourage you to take this matter very seriously and inform us if any support is required as we will be more than happy to arrange that for you.
Best regards,
[Your Name]
[Your Job Title]
[Company Name]