I'm pretty sure that I know a word for a person who takes leave without informing in advance but I am not able to recollect it.
Don't count on him to finish the work today. He is a _______.
"We don't encourage people who are _________. Serious actions will be taken against them", said the manager.
An absentee is a person who is expected to be there but they're not. But the person might have given a heads up that they will be absent. So that doesn't fit well.