If you unable to work due to any illness or injury lasting fewer than seven days you do not need a doctor’s sickness certificate.
Your employer may ask you to complete a self-certification form (SC2) which is available from your employer or on the HMRC website.
Evidence 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).
A medical certificate, now called a 'Statement of Fitness for Work’, 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. Your employer may still ask for a medical certificate from your GP.
It is up to your employer to decide if you are incapable of work.
Statement of Fitness for Work - ’Fit Note'
The 'fit note' was introduced in 2010. The note will help you return to work sooner by providing your employer with more information about the effects of your illness or injury, so they can support you.
You can find more information on the Direct.Gov website.