You do not require a doctor's medical 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.
We make a charge for doctor's medical certificates required for (appropriately taken) time off during the first 7 days of illness.
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'
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.
For more information see the DirectGov website (where this information was sourced)
Medical Evidence for where an employee is advised to stay at home due to an infectious disease
By Law, medical evidence is not required for the first 7 days of sickness. After 7 days, it is for the employer to determine what evidence they require, if any, from the employee. This does not need to be a fit note (MED3) issued by a GP or any other doctor. Your employee will be advised to isolate themselves and not to work in contact with other people by NHS 111 or Public Health England if they are a carrier of, or have been in contact with, an infectious or contagious disease, such as COVID-19. We strongly suggest that employers use their discretion around the need for medical evidence for a period of absence where an employee is advised to stay at home due to suspected COVID-19, in accordance with the public health advice being issued by the government.