[bbarn]

As others have said - it's invasive, and probably illegal.

BUT - I feel like we're missing some context here. Is your reason for refusal based solely on privacy concerns, or that you don't want them to know you see a psychiatrist? Have you been underperforming and used your ADHD as justification/excuse as to why and they want some proof of that?

You're mentioning the ADHD, so it must be relevant in some way, otherwise the post would simply be "My company wants my medical records, should I allow it?"

[burnoutgal]

There's no "but", it's invasive and illegal. The boss is using OP's ADHD as an excuse to demand all this private information, to "prove" they need accomodation.

[d1sxeyes]

Better not to talk in absolutes. The broad scope of this is so unusual that I can't imagine any 'large organisation' with an HR department requesting it without being sure of their grounds in advance. Obviously, they may be wrong, but I doubt this has come from nowhere.

Without any context, it does seem as though this would be illegal in my jurisdiction. However, OP mentions that the request is authorisation for HR, to request medical information, which suggests someone has already reviewed this from HR and it's possible they're more familiar with the law than you or I are in terms of what they can and can't ask for. Especially the 'twelve (12)' stinks as though it's been drafted by a lawyer.

That said, normally a 'fitness to work' proceeding in my jurisdiction would not be entitled to future medical records, and the medical records would be reviewed by first your local GP, and then eventually potentially a government occupational health authority, and would never be passed to the employer.

If this were me, I would most certainly refuse. I would instead offer to provide a statement from my doctor that I am fit to work. I can't see any way that this arrangement could possibly benefit OP.

[asteroidbelt]

Yes, knowing the context would be interesting although probably irrelevant to the answer.

I’d just quit, but calling a lawyer sounds right too.

But for example it would be reasonable (albeit inappropriate) to ask medical records of someone taking paid sick days too often.

[progman32]

I suspect quitting leaves settlement money on the table. Not saying that's unreasonable, that's for everyone to decide for themselves and their situation. But the key imo is to lawyer up before taking any drastic action...