In the UK, you can self-certify sickness for up to 7 calendar days (including weekends and bank holidays). This means you can inform your employer that you are unwell and do not need to provide a doctor's fit note for the first 7 days of absence. After 7 days, if you need to remain off work, a fit note (sometimes called a sick note) from a registered healthcare professional is required as proof of illness. Self-certification allows employees to manage brief illnesses simply, but beyond 7 days, medical evidence is needed to continue the sick leave officially. Employers cannot request a fit note before 7 days of sickness absence. Fit notes can typically cover absences for up to 3 months in the initial period of illness, and Statutory Sick Pay (if applicable) can last up to 28 weeks. Therefore, self-certification can be used only for short-term sickness of 7 days or less. For longer sickness periods, a fit note is necessary.