Functional Behaviour Assessment (FBA) on the NDIS, Explained

Families hear “we’ll start with an FBA” and nod, then go home wondering what they just agreed to. I’m Yos, an NDIS behaviour support practitioner working with young people aged 12 to 20 across Western Sydney, South West Sydney and the Illawarra. Here’s what a functional behaviour assessment is, what you’ll be asked, and what you should get at the end.

What is a functional behaviour assessment?

A functional behaviour assessment (FBA) works out why a behaviour keeps happening. Every behaviour does a job for the person. It might get them something they need, get them away from something that’s too much, or help them feel okay again. The FBA is how a practitioner works out that job.

On the NDIS, the FBA is one part of a wider behaviour support assessment. The NDIS Commission says a comprehensive behaviour support plan has to be based on that assessment, so the plan rests on an understanding of what’s happening and why.

Who can do an FBA on the NDIS?

Only an NDIS behaviour support practitioner, working through a provider registered for specialist behaviour support (registration group 0110). You can check both on the NDIS Commission’s website. Our guide to what a PBS practitioner does shows you how.

What happens during an FBA?

The practitioner gathers information from a few directions and then looks for the pattern.

• Talking with the young person. What’s hard for them, what helps, what they’d change. With teenagers, this comes first and it takes time.
• Talking with family, school and the support team. Each person sees a different part of the week.
• Reading what already exists. Reports from doctors, psychologists, speech and OT, school plans, incident records.
• Observation. Seeing the young person at home, at school or in the community, in the settings where things are hardest.
• Simple data. Short notes on what happened before, during and after a hard moment. A good practitioner gives you a format you can fill in on a phone in 30 seconds.
• Health. Pain, poor sleep, hunger or a medical issue nobody has picked up can drive behaviour. That gets checked early.

What do you get at the end?

A written assessment that explains the behaviour in plain language: when it happens, what sets it off, what keeps it going, and what need it’s meeting. It should be written as a hypothesis, something like “the information so far suggests…”, because it gets tested once the plan is running.

It should also name the young person’s strengths and what’s already working. Those become the building blocks of the plan.

How long does an FBA take?

It depends on how complex things are and how quickly information comes in. The Commission’s timeframe is the guide here: if there’s an immediate need, an interim plan comes within 1 month of the provider being engaged, and the comprehensive plan, built on the assessment, within 6 months. The interim plan keeps everyone safe while the assessment is done. Our behaviour support plan guide explains the difference between the two.

How does the FBA shape the plan?

Every strategy in the comprehensive plan should link back to what the FBA found. If the assessment shows a young person melts down after school because the bus ride drains them, the plan might change the trip home, build in quiet time, and teach a way to ask for a break. If a strategy doesn’t connect to the function, ask why it’s there.

If the plan includes any regulated restrictive practice, it’s lodged with the NDIS Commission, with the FBA attached where relevant.

How can families help?

• Share the reports you already have early, even old ones.
• Tell the practitioner about the good days too, and what was different.
• Keep the data notes simple and honest. Missed days are fine.
• Ask how your young person will have a say in the assessment and the plan.

Frequently asked questions

What is a functional behaviour assessment on the NDIS? It’s the part of a behaviour support assessment that works out what a behaviour is doing for the person. The comprehensive behaviour support plan is built on it.

Who can do a functional behaviour assessment? An NDIS behaviour support practitioner, working through a provider registered for specialist behaviour support (registration group 0110).

Is an FBA the same as a diagnosis? No. Doctors and psychologists diagnose. An FBA explains a behaviour so the plan can meet the same need in a better way.

Does an interim behaviour support plan need an FBA? No. An interim plan focuses on safety and lowering risk while the assessment is done. The comprehensive plan is the one built on the assessment.

How is an FBA funded? From the Behaviour Support budget in the NDIS plan (Improved Relationships on older plans), which pays for assessment, plan development and training.

General information, checked against NDIS Commission guidance on 3 November 2026. Written by Yosmerys Aparicio Cuencas, NDIS behaviour support practitioner and founder of Supporting Communities Australia.