Fit Notes (previously known as 'sick notes')
You do not require a doctor's 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.
For most people getting back to work as soon as possible is good for your health. Fit Notes can include extra information to help your employer support your return to work.
Evidence that you are sick
Please note that certificates cannot be dated in the future and can take up to three days to process.
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 or other health care professional. 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.
For more information see the DirectGov website.