You do not need a sickness certificate for statutory sick pay unless you have been absent from work for 7 days. Employers who insist on having one earlier will have to pay a fee.
Certain types of medical certificates/examinations are not provided free under the National Health Service. Your Doctor will charge a fee for insurance medicals and examinations for fitness to drive (HGV, PSV) and for certificates required by employers, e.g. Police, Teachers etc. (see Fees and Charges section).
