If you’re off work
A doctor’s sickness certificate is NOT required 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
If you are sick for more than 7 days, your employer may ask you for medical evidence to support payment of SSP (statutory sick pay). A 'Statement of Fitness for Work’ from your doctor is evidence that you are sick and would normally be accepted by your employer, unless there is evidence to prove otherwise. The ‘Statement of Fitness for Work’ 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. In normal circumstances an appointment with the GP would be necessary to obtain this statement.