What is a Functional Behaviour Assessment (FBA)? A Plain-English Guide for NDIS Families

If you've been told that your family member needs a Functional Behaviour Assessment before a Behaviour Support Plan can be developed, you might be wondering what that actually means and what to expect. This guide walks you through the process from start to finish.

What is a Functional Behaviour Assessment?

A Functional Behaviour Assessment — usually called an FBA — is a structured information-gathering process carried out by a registered Behaviour Support Practitioner. Its purpose is to understand the function of a behaviour: in other words, what purpose the behaviour serves for the person doing it.

This might sound like a simple question, but it's at the heart of effective behaviour support. A behaviour that looks the same on the surface — for example, a child hitting out — might be happening for very different reasons in different children. One child might be seeking sensory input. Another might be trying to escape a task they find overwhelming. A third might be trying to communicate something they don't have the words for. Treating all three the same way would be ineffective and potentially harmful.

What does an FBA involve?

Every FBA is different because every person is different. But the process typically involves a combination of the following:

Interviews and conversations

The practitioner will spend time speaking with the people who know the participant best — family members, carers, teachers, and other support workers. These conversations gather important context: the history of the behaviour, when it typically occurs, what seems to trigger it, how the people around the participant respond, and what has and hasn't worked in the past.

Direct observation

Where possible, the practitioner will observe the participant in the environments where the behaviour most commonly occurs — at home, in the community, at school, or during daily activities. Observation provides information that interviews alone can't capture.

Review of existing records

The practitioner will review any existing reports, assessments, incident records, or clinical documentation that are relevant to understanding the behaviour. This might include previous psychological assessments, school reports, or medical information.

Data collection

Carers and support workers may be asked to complete simple ABC charts (Antecedent–Behaviour–Consequence) or frequency records over a period of time, recording what happens immediately before and after the behaviour occurs. This data helps identify patterns that might not be obvious from a single observation.

What happens after the FBA?

Once the assessment is complete, the practitioner analyses all the information gathered and develops a hypothesis about the function of the behaviour — the most likely explanation for why it is occurring. This forms the foundation of the Behaviour Support Plan, which outlines the proactive strategies, skill-building goals, and environmental changes that will address the behaviour at its root cause rather than simply reacting to it after the fact.

Who can conduct a Functional Behaviour Assessment?

Under the NDIS framework, Functional Behaviour Assessments must be conducted by a registered Behaviour Support Practitioner. Practitioners are assessed against the NDIS Behaviour Support Capability Framework and work at different proficiency levels — Core, Proficient, Advanced, or Specialist — depending on their qualifications, training, and supervised experience.

The complexity of the behaviour and whether restrictive practices are involved will influence which proficiency level is required. If you're unsure about a practitioner's qualifications, it is entirely reasonable to ask them to confirm their NDIS practitioner registration and proficiency level.

How long does an FBA take?

This varies considerably depending on the complexity of the situation, the availability of key informants, and whether direct observation sessions are required. As a general guide, the information-gathering phase typically takes between two and six weeks, with additional time required to analyse findings and develop the written report and plan.

Where behaviours pose an immediate risk to safety — for example, where self-injury or aggression towards others is occurring — an interim Behaviour Support Plan may be developed quickly to provide immediate guidance while the full assessment continues.

What does a good FBA look like?

A thorough Functional Behaviour Assessment should:

• Be genuinely participant-centred — taking the time to understand the person's communication style, sensory needs, history, and preferences
• Involve the people who know the participant best, not just brief conversations with one or two people
• Result in a clear, evidence-based hypothesis about the function of the behaviour
• Be written in plain language that families and support workers can actually understand and use
• Form the basis of strategies that are realistic and achievable in the participant's actual life, not just in theory

Is an FBA always required before a BSP?

Under the NDIS Quality and Safeguards Commission's requirements, a Behaviour Support Plan should be based on a thorough functional assessment. Where restrictive practices are involved, a comprehensive assessment is required. In some cases — particularly where behaviours present an immediate safety risk — an interim plan may be developed to provide urgent guidance while the full assessment is completed.

How Aceso Therapy approaches FBAs

At Aceso Therapy, Functional Behaviour Assessments are conducted by Shilpi Ashta, a Specialist Behaviour Support Practitioner (Advanced). Shilpi works collaboratively with families, support teams, and schools to build a thorough picture of the participant before developing any strategies — because good support is built on genuine understanding, not assumptions.