If someone is too late to pray Fajr because he overslept due to long work hours is it permissible to perform the prayer later in the morning after waking up?
It is not allowed for a Muslim to deliberately delay his Prayer till its time goes away. Muslim must do every thing possible to wake up and perform Fajr Prayer withing its time.
If he is ill and could not get up for the Prayer, he must perform it as Qadha later on.
Wassalam.