The doctors do not have to issue a sick note for the first 6 days of sickness. Please ask your employer for an SC2 form (self-certification) to cover you for this period. A private sick note can be issued for insurance purposes at a minimum fee of £15.
If you are still sick after 6 days, please make an appointment with a doctor if you require an NHS free sick note. If your illness extends beyond the period certified by the doctor, you will need to see the doctor again for an extension.
An appointment with the doctor is also required if you have been asked to obtain a Med 4 certificate.
Download SC2 = 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 form yourself when you return to work. This is called self-certification.
If you're sick and off work for more than seven days, your employer will probably ask for proof of your illness. Most employers ask for a fit note from your GP.
However, this will also depend on your employer's company policy on sick leave (or sickness absence). This policy should tell you how many days you can be off sick before you need to provide proof of illness or a fit note.
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)