Sounds like you need to change employers.
During my career I was never asked to provide proof of appointments such as dentist , doctors , eye tests etc.
When your employed you are put in a position of trust, that works both ways. If as an employer , manager , team leader etc , you don't feel you can trust an employee , then you have a bigger issue than prooof of the odd GP apppimtmemt.
But then again I did work in IT where.we supported multi billion dollar financial systems. Later when I was leading a team , I had to trust the professionals I had employed.