You do not require a doctor’s sickness certificate for any illness lasting seven days or less.
Your employer may 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
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).
Your employer can ask you to confirm that you’ve been ill.
You can do this by filling in a self-certification form yourself when you return to work.
If you’re sick and off work for more than seven days, your employer will probably ask for proof of your illness.
Employers usually ask for a fit note 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 your illness or injury.
For more information see the DirectGov website (where this information was sourced)