[Chilli-pepper]

I would imagine that this request will be treated as a private request and the GP would/could charge for this letter.

As masks are no longer a legal requirement there is no need for any exemption letter from a GP- if this is a rule/request of the company it will be treated as no different than a company asking for any other medical exemption letter or medical test/exam or report from a GP for a job, which is chargeable.