A 'Fit for work' certificate, which replaced the old sickness certificate, will not be issued for any illness lasting seven days or less. Your employer may, however, require you to complete a self-certification form (SC2), which is available from your employer (or by clicking here to complete). For any illness lasting longer than seven days you will need to see your doctor for them to issue your certificate. Subsequent renewals may be possible by telephone - your doctor will advise.