Have you been off work?
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.
COVID19 ISOLATION NOTES
In light of the COVID19 virus some employers may ask for a sick note if you are isolating. If you have to stay at home but feel well enough to work, ask your employer if you can work from home - in this case you will not need an isolation note. Otherwise, below are two links - the first is a downloadable letter for you to complete if you are self-isolating but have not spoken to a medical professional. The second is the link to the NHS 111 website, which you should use if you have been in contact with a GP or the 111 service regarding self-isolation.
Medical certificate for employer
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)