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).
However, this will also depend on your employer's sickness absence policy. The policy should tell you how many days you are allowed to be off sick before proof of illness or a Fit Note stating that you were unable to work is required.
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 Statutory Sick Pay (SSP). This will usually be a Fit Note stating that you were too ill to work at all.
If appropriate to the reason for your absence, 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.
If your employer refuses to accept an SC2 for a period of sickness absence lasting seven days or less, we are able to provide you with a Private Sickness Certificate for a charge of £63, to be paid to reception at the time of collecting the note. The cost of this note may be redeemable from your employer.
It is not practice policy to issue medical certificates or letters to patients who request these after they have missed an important legal commitment, such as a court date or a probation attendance. Requests for medical evidence to support failure to attend must be made before the date of attendance and as soon as the patient could reasonably anticipate missing the date of the legal commitment. Medical evidence will only be provided when the patient directly consults with the doctor, unless they have attended hospital. In some cases a discussion may need to take place between the doctor and the patient's lawyer or probation officer, before a decision to provide medical evidence can be made.
Statement of Fitness for Work - ’Fit Note'
The Fit Note, introduced on 6 April 2010, not only allows your doctor to state that you are unable to work at all, but can also state that although you are not fully recovered, you are able to return to work on an agreed date provided your employer makes some changes to your working hours and/or to your working practices. The duration of these changes and what they should be can be specified in the note and can incorporate discussions you have already had with your employer as to how they will facilitate your gradual return to work. It is not Practice policy to issue a 'Fit to return to work' certificate.
Please read this guide for more information about what the different sections on your Fit Note mean, and how you can use it to talk with your employer about returning to work - The Fit Note.
For more information see the DirectGov website (where this information was sourced)
Sick Notes following Hospital Treatment
If you have been treated in a hospital, it is the responsibility of your consultant to issue a Sick Note that will cover you for the entirety of the period during which it is anticipated you will not be able to return to work. Please do not book a doctor's appointment to request a sick note following hospital treatment, as this will be refused.