There are a wide variety of reasons why employees may decide to take unplanned leave, including:
There is also the case of employees being absent for no given reason, or more commonly where they claim a reason (normally sickness) but this is not always true.
If an employee is sick for a maximum of seven days in a row (including weekends and bank holidays) they do not need a note from the doctor, but their employer can ask them to fill out a form to confirm that they were sick; this is known as self-certification. Employees who are sick for more than 7 days consecutively can be asked to provide a 'fit note' from their GP.
It should be noted that mental illness and even stress at work (eg caused by bullying, harassment or excessive workload) can lead to sickness absence, and employers should not treat mental illness any less seriously than physical forms of sickness.
For more information read Managing sickness absence and create your Sickness policy.
For rules and policies surrounding planned leave read:
In situations where absence is not planned, employees are entitled to reasonable time off to deal with emergencies involving dependants (eg child, grandchild, parent, partner or spouse etc). Emergencies include:
Employers are not obliged to pay employees in respect of emergency time off, subject to the employment contract or policies on compassionate leave.
Employees are also entitled to time off for bereavement (eg to attend a funeral) but this does not have to be paid. However, there are government plans to provide up to two weeks' paid leave for parents who lose a child under the age of 18 to allow them time to grieve. This is expected come into force in the future.
Long term absence will normally fall into the context of long term illness. A return to work plan can be agreed between long-term sick employees and their employer which avoids the need to keep obtaining fit notes.
Persistent or intermittent absence (ie where an employee keeps taking short amounts of time off for sickness or another reason) should be monitored and assessed over time.
Employers should consider if long-term sickness or persistent short-term sickness constitutes a disability; if so, they may be required to make reasonable adjustments.
Ultimately, employers can dismiss a long-term sick employee. However they must first consider if the employee is able to return to work (eg in a more flexible capacity) and they should also consult with the employee regarding the outlook of their condition and their prospect of returning to work. For employees who are persistently absent (due to illness or for other reasons), care should be taken when considering dismissal and the relevant internal policies should be followed.