If you fall ill while you are on your annual leave, you will need to visit a doctor and obtain a medical certificate certifying that xxx date to xxx date the employee was medically unfit for work.
Once you return from annual leave, you will need to show your medical certificate to your employer and the employee is entitled to convert those sick days from annual leave to sick leave and your annual leave entitlement must be credited accordingly.
Important: A medical certificate must be presented to your employer! Failure to present a medical certificate will mean that you were still fit for work and is therefore not entitled to sick leave if not declared unfit for work.
Information provided by The South African Labour Guide.