It seems obvious to employers that employees need to show up for work when they are scheduled, but it doesn’t always work that way. It is reasonable to have attendance policies, requiring employees to show up or otherwise meet their employment obligations. This could take the form of a job abandonment policy such as this:
Attendance is an essential function of all jobs at Company. If an employee is absent without notice, they may be deemed to have abandoned their job and voluntarily terminated their employment with Company.
Many policies on absences or job abandonment will say “if an employee is absent for more than three days without notice”, but it is better not to put a time limit on it. “May be” allows management discretion: someone who swears at the boss and stomps out angrily can be assumed to have quit immediately, whereas someone hunting who isn’t back on the expected date may be stuck in the backcountry and not intending to quit at all. A doctor’s note after the fact generally counts as notice, so don’t move hastily if there is no communication on the first day of absence.
Attendance gets a little trickier when you are dealing with accommodations for disabilities or pregnancy, but you can still require “predictable attendance”. You don’t have to accommodate erratic, unpredictable attendance. Before deciding how to handle attendance in this case, be sure you have thought through whether or not it is an essential function of the job. For someone who works a customer-return desk in a store, it is hard to argue that they can do the job from home or on flexible hours; attendance is an essential function. On the other hand, for someone who does data entry, flexible hours or telecommuting may make sense and be a reasonable accommodation.
The best reason for requiring attendance is so that employees can get their work done. Take some time to think through how essential it is for employees to show up in the office every day so that you have an idea how much flexibility you have to help them meet what life throws at them.