Sickness Certificates
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.
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.
Hospital Discharges
If you have been discharged from the hospital, your hospital team will issue any fit notes for the entire period of your recovery. Please contact the ward staff (even after discharge) if this has not been done.

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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).
Extending sickness certificates
If you have a sickness certificate which is running out but you feel you are still not fit to return to work, you will need to contact our admin team on the day that your current note runs out, or on the next working day if this falls on a weekend.
Please be aware that sickness certificates can always be backdated, but GPs are unable to forward-date them so you are unable to request a renewal before your current one runs out.
Renewal requests for sickness certificates will be processed by the doctor within 5 working days.