Seven days off sick or less
If you're off work sick for seven days or less, your employer shouldn't ask for medical evidence that you've been ill. Instead they 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.
You can complete the SC2 self-certificate form here
Some employers will request a Doctor’s note regardless. A private doctor’s note may incur a charge.
More than seven days off sick
If you're off work sick for more than seven days your employer will normally ask for a fit note (or Statement of Fitness for Work) from your GP or hospital doctor. Fit notes are sometimes referred to as medical statements or a doctor's note.
If you have attended the hospital and the consultant recommends that you have time off work, he/she will issue the fit note for the duration of your illness or convalescence.
For more information about Fit Note please click on the following link.