From the 24th July 2020 the government require face coverings to be worn on public transport and in shops.
There are some people who are exempt. You do not need certification from a Doctor for exemption in general terms, and if an employer or other service required medical certification then a fee will apply.
For public transport, First Bus have a card/badge you can print yourself at home:
For general use there are some helpful self-print resources here:
Regrettably we are not able to provide printing services, but these may be obtained via the city councils community hubs.