You can ask, but cannot require it: disability under the Equality Act 2010 needs no formal diagnosis, so withholding adjustments for lack of proof risks discrimination. With consent, seek an occupational health view.
Why a diagnosis is not the test
A person is disabled under the Equality Act 2010 if they have a physical or mental impairment that has a substantial and long-term adverse effect on their ability to carry out normal day-to-day activities (section 6). That test is about how the condition affects the person, not about whether a clinician has put a name to it. So an employee can be disabled in law, and protected, without ever holding a diagnostic letter. If you make "proof of diagnosis" a precondition for reasonable adjustments, you are gatekeeping a right behind a document the law does not ask for, which is where a disability-discrimination claim starts.
You may already be on the hook to act
The duty to make adjustments arises once you know, or could reasonably be expected to know, that someone is disabled. The Equality and Human Rights Commission's statutory Employment Code calls this constructive knowledge: you have to do all you can reasonably be expected to do to find out, and knowledge held by your occupational health provider or HR is generally treated as yours. So if an employee has told you they are struggling, or the signs are there, demanding paperwork before you engage does not pause the duty. It can deepen the problem, because a tribunal may find you should have known already.
How to seek evidence lawfully
Asking is fine; how you ask is what matters. Acas, the UK workplace-advice body, says nobody has to tell their employer they are disabled, and that when adjustments are requested you should listen and not make assumptions. Where you genuinely need a clinical view to decide what helps, the right route is an occupational health referral made with the employee's consent, not a demand for their medical records. Two things to hold in mind:
- Occupational health gives you a functional opinion on what the person can do and what would help, not necessarily a diagnosis. That is what you need to act.
- Any health information you collect is special category data under the UK GDPR. The ICO is clear you need an Article 9 condition to process it, and that consent is often hard to rely on at work because of the power imbalance, so do not treat a blanket demand for records as lawful.
Why this matters for you
Getting this wrong runs two risks at once. Refuse or delay adjustments because no diagnosis was produced and you risk a discrimination claim and a breach of the duty. Over-collect health data to cover yourself and you risk a data-protection breach. The safe path is the narrow one: respond to the need you have been told about, and seek only the functional evidence you actually need, with consent.
Where the law comes from
Related
This page is general information, not clinical or legal advice.