You do not require a Med3 Fit Note (often referred to as 'sick note') 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, on the HMRC website, or by clicking the link below (printable version).
Statutory Sick Pay (SSP) Employee Statement of Sickness
Evidence that you are sick
If you are sick for more than seven days, your employer can ask you to give them some form of 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.
Statement of Fitness for Work - ’Fit Note' Med 3 Form
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.
Please allow 24 hours, after a request, for your Fit Note to be ready for collection.
For more information see the DirectGov website (where this information was sourced)