For the first four days of any illness you do not require any form of certification. It is for you to decide if you are fit for work.
For the next three days (including Saturdays and Sundays) you must fill in a self-certification form (SC2) which is available from your employer or here.
After the first seven days your employer may ask you for a medical certificate (Form MED3) from your doctor. Medical certificates are also called sick notes or Doctor's statements and are provided free of charge.
Please note your GP will not issue a medical certificate for an illness of less than 7 days duration. Certificates cannot be back-dated unless a doctor or nurse has seen you at the time of incapacity you need the certificate to cover.
Occasionally your employer will insist on medical evidence for your absence when it has been less than 7 days duration. Unfortunately in these circumstances we charge an administration fee for producing a letter detailing the reasons for your absence from work. Fees available on request.