If you are forced to take time off work due to your health needs then you may be required by your employer to provide evidence of your condition for their absence monitoring procedure. In most cases you will then need to provide one of the following:
Self-Certification (7 days or less)
In most instances of short-term absence you do not need to contact your doctor. You do not require a doctor's sickness certificate for any illness lasting seven days or less. Your employer may however require you to complete a self-certification form (SC2) which is available from your employer or on the HMRC website.
Please note that a GP will not issue a certificate for absences less than 7 days if requested by an employer, as the above is sufficient and this is an inefficient use of valuable GP time.
Statement of Fitness for Work (MED3)
If you are sick for more than seven days, your employer can ask you to give them some form of additional medical evidence to support payment of SSP (statutory sick pay).
It is up to your employer to decide whether you are incapable of work. A medical certificate, now called a 'Statement of Fitness for Work’ (see below) from your doctor is strong evidence that you are sick and would normally be accepted, unless there is evidence to prove otherwise.
You could also provide evidence from someone who is not a medical practitioner, e.g. a dentist. Your employer will decide whether or not this evidence is acceptable. If your employer has any doubts, they may still ask for a medical certificate from your GP.
Return to Work Note - "Fit Note"
The 'fit note' was introduced on 6 April 2010. With your employer's support, the note will help you return to work sooner by providing more information about the effects of your illness or injury.
This may include an indication on the roles you may be suitable for and any reasonable adjustments made in agreement with your employer.
For more information see the DirectGov website (where this information was sourced)