You do not require a doctor’s sickness certificate for any illness lasting 7 days or less.

You can complete a self-certificate form yourself. Lots of employers will have their own self certification forms, however if they don’t, you can complete a form by following the link below and giving it to your employer: LC Forms (hmrc.gov.uk)

For any illness lasting longer than 7 days you will need to see/speak with your GP for them to issue a sickness certificate and for any subsequent renewal of the certificate.