Evidence that you are sick less than 7 days
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.
Evidence that you are sick for 8 or more days
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.
On-going evidence that you are sick (after the first Statement of Fitness for Work expires)
Please make a telephone appointment to discuss this with a Doctor. They will decide when they talk to you if they actually need to see you. Please give us a few days notice so your 'Statement of Fitness for Work' does not run out.
Statement of Fitness for Work - ’Fit Note'
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. Many of these can be provided after a telephone consultation, try this first. The Doctor will decide if they need to see you after talking to you.
For more information see the DirectGov website (where this information was sourced).