Money
The number nobody puts on their home page. Here it is, with what moves it and what you can realistically claim back.
Adult Autism Assessment Perth arranges autism and ADHD assessments for adults and adolescents across Perth and WA. An adult autism assessment in Australia generally runs between roughly $1,500 and $2,500. Adding an ADHD assessment at the same time typically adds a few hundred dollars rather than doubling it, because the developmental history is shared.
These are indicative figures for budgeting. The exact price is confirmed in writing before an assessment is booked.

For adults, a diagnostic autism assessment is generally not covered by Medicare. The items that exist for autism assessment are aimed at children, with age limits that most adults reading this have passed.
A Mental Health Care Plan from your GP can rebate treatment sessions, which is a different thing from the assessment itself. Anyone implying that an adult assessment is largely covered by Medicare is, at best, being loose with the truth.
Extras cover sometimes contributes toward psychology sessions, and sometimes excludes assessment specifically. It depends on your fund and your policy tier. Ring your fund and ask about the specific item numbers your clinician will use — that is the only answer that binds anyone.
The fee is not for the appointment. Roughly, it covers a 2–3 hour clinical interview, the scoring and interpretation of standardised instruments, the review of any history and documents you provide, and the writing of a comprehensive report — which is usually the largest single block of time and happens after you have gone.
A cheap assessment is generally cheap because the report is short. That is the part you will still be using in five years, so it is the wrong place to economise.
The short version: a diagnostic autism assessment for an adult is generally not claimable on Medicare, a Mental Health Care Plan rebates treatment rather than assessment, private health extras vary and frequently exclude assessment, and the NDIS does not fund the diagnosis that establishes eligibility.
The full detail, including exactly what to ask your fund, is on Medicare and rebates.
That is your call and we are not going to pretend otherwise. What we can say is what people tell us they got for the money: workplace adjustments that actually stuck, a stop to being treated for the wrong thing, and in many cases the first coherent explanation of their own life they have ever been offered. None of that is guaranteed, and a report is not a solution on its own.
Tell us where you are and what you are after. No cost, no obligation, and no need to be certain before you ask.