Both give an equally valid UK diagnosis; the real difference is cost and speed. The NHS is free but waits often run 1-3 years, while a private assessment costs roughly £1,800-£3,500 as of 2026 and takes weeks.
The difference that actually matters
Clinically, the two routes aim for the same standard. The UK guideline that sets out how a child should be assessed (NICE CG128, for under-19s) applies whether the work is done by an NHS team or a private one, so a diagnosis from either is a real diagnosis. What you are really choosing between is a free assessment with a long wait and a paid one with a short wait. There is no basis in law for a school or council to reject a report simply because you paid for it: the SEND Code of Practice 2015 treats professional evidence on its merits, not on who funded it.
NHS vs private autism assessment, side by side
| What you are comparing | NHS | Private |
|---|---|---|
| Cost | Free | Roughly £1,800-£3,500 for a child (2026); multi-disciplinary assessments cost more |
| Waiting time | Often 1-3 years, varying widely by area | Typically a few weeks to a few months |
| Who carries it out | A multi-disciplinary NHS autism team | A clinician or team you choose; check their registration and methods |
| Accepted by school and for an EHCP | Yes | Yes, if it follows NICE guidelines and uses recognised tools |
| Follow-up support | Usually links into local NHS and CAMHS pathways | Varies; reports, advice and follow-up may be charged separately |
The catch with going private: it has to be done properly
A private diagnosis only carries weight with your GP, your child's school and a future EHCP if it is done to the standard the NHS expects. Before you book, ask the provider in writing to confirm that the assessment:
- follows NICE guidelines and uses recognised tools (such as the ADOS-2, ADI-R or DISCO);
- is carried out by suitably qualified, registered clinicians;
- draws on more than one source, ideally a multi-disciplinary assessment, not a single short online session.
A quick, single-questionnaire "diagnosis" bought online is the one most likely to be questioned later, which can leave you paying twice.
When each route makes sense (and the middle option)
Go NHS if cost is the deciding factor and you can manage the wait with support in place at school meanwhile. Go private if a faster answer would bring support, school cooperation or your own peace of mind sooner, and you can afford it. There is also a middle path in England: Right to Choose lets you pick an NHS-funded provider, often with a shorter wait. It is well established for adults; availability for children varies by area, so ask your GP directly.
Where the law comes from
Related
This page is general information, not clinical or legal advice.