I am writing because you have not attended work since [date] and we have not received an explanation for your absence or been able to establish contact with you.
Our records show that you were expected to attend work on [dates / shifts] but did not do so. You have not followed the Company's normal procedure for reporting sickness or other absence and, at present, your absence is therefore being treated as unauthorised.
We are concerned about your absence and also want to make sure that there is no reason for you being unable to contact us that we need to be aware of.
What you need to do
Please contact [name / department] as soon as possible, and no later than [date / time], to explain the reason