By national agreement the DSS does not provide a sick note for an illness of up to seven days. A self-certification form can be obtained from your employer. Illnesses of more than seven days may require a doctor’s certificate and you will need to make an appointment unless you have been seen, for example, at casualty or hospital, in which case a note can usually be issued on the basis of their report.
When do I need a fit note?
The NHS advice for patients titled When do I need a fit note? is a useful guide