About charging fees:
The NHS provides most health care free of charge. However there are a number of other services for which fees can be charged. These are mainly for services not covered by the NHS, such as medical reports for insurance companies.
Doctors are involved in a whole range of non-medical work, largely on the basis that they occupy a position of trust within the community, and are in the position to verify the accuracy of information. If a GP signs a certificate or completes a report, it is a professional duty that s(he) checks the accuracy of such information. This may involve examining the patient's entire medical record.
What certificates do I have to pay for?
There are a number of certificates which GPs are obliged to provide free of charge. These include certain certificates supporting claims by patients for social security benefits.
If a patient is off work for seven days or less the GP does not have to provide a sick note. A patient can be refused a note or charged for a private one for illnesses of seven days or less.
Please see Fees for services not provided under the NHS