Autism Spectrum Disorder (ASD) affects an estimated one in 40 Australians. It is one of the most common presentations in the NDIS and one of the most complex to assess for funding purposes. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) classifies ASD into three severity levels, each describing a different level of support required. Understanding what these levels mean clinically, how they interact with NDIS eligibility and what a Functional Capacity Assessment provides at each level is essential knowledge for anyone navigating the NDIS with an ASD diagnosis.

What is Autism Spectrum Disorder?

Autism Spectrum Disorder is a neurodevelopmental condition characterised by differences in two core areas under DSM-5. The first is persistent deficits in social communication and social interaction across multiple contexts. The second is restricted, repetitive patterns of behaviour, interests or activities. Both must be present for a diagnosis of ASD.

The term spectrum reflects the significant variation in how ASD presents across individuals. ASD does not describe a single, uniform presentation. It encompasses a wide range of profiles, from individuals who communicate verbally, live independently and are employed, to individuals who have no functional speech, require full personal care support and cannot safely access the community without continuous supervision. The diagnostic levels provide a broad framework for describing this variation.

ASD is a lifelong condition. It is not caused by parenting, vaccination or environmental factors. It is not something a person grows out of. The functional presentation of ASD can change across the lifespan, particularly at major developmental transitions, but the underlying neurodevelopmental difference remains permanent. This permanence is a key factor in NDIS eligibility.

How ASD is diagnosed

A diagnosis of ASD is made by an appropriately qualified clinician on the basis of the DSM-5 criteria. In Australia, ASD can be diagnosed by a paediatrician, psychiatrist, clinical psychologist or a multidisciplinary team. The diagnosis involves a clinical interview, behavioural observation, standardised assessment tools and collateral history from parents, carers, teachers and other people who know the individual across different settings.

The DSM-5 diagnostic criteria require that symptoms be present in the early developmental period, even if they do not fully manifest until later when social demands exceed the person’s capacity. This is particularly relevant for adults with Level 1 ASD who may have managed in structured settings during childhood but begin to struggle significantly in adulthood as the demands of independent living, employment and relationships become more complex.

At the time of diagnosis, the clinician assigns a severity level to each of the two core domains: social communication and interaction, and restricted and repetitive behaviours. These levels can differ within the same individual. A person may have Level 2 difficulties in social communication and Level 1 difficulties in restricted and repetitive behaviours, or the reverse. The diagnostic level reported is typically the higher of the two.

The three DSM-5 severity levels in detail

The DSM-5 describes three levels of ASD severity. These levels describe the amount of support the person requires at the time of diagnosis. They do not describe intelligence, potential, life outcomes or the extent to which a person can develop skills and independence over time. Two people with the same diagnostic level can have very different functional profiles and very different daily support needs.

Level 1: Requiring Support

Social communication: Difficulty initiating social interactions. The person may attempt social contact but in ways that are unusual or unsuccessful. Reduced interest in or ability to engage in back and forth conversation. Difficulty interpreting social cues, unspoken rules and the expectations of different social environments. May appear to manage independently in familiar, structured settings but experiences significant difficulty in unstructured, unpredictable or socially complex environments.

Restricted and repetitive behaviour: Inflexibility of behaviour causes significant interference with functioning in one or more contexts. Difficulty switching between activities. Problems with organisation and planning affect independence. These difficulties are noticeable to others.

NDIS eligibility: Level 1 ASD is included in NDIS Condition List B. NDIS eligibility is not automatic. Functional evidence of substantially reduced functional capacity across one or more NDIS functional domains is required.

Level 2: Requiring Substantial Support

Social communication: Marked deficits in verbal and non-verbal social communication skills. Social impairment is apparent even with supports in place. Limited initiation of social interactions. Reduced or atypical responses to social approaches from others. Communication is simple and concrete. Social interactions are limited to very narrow special interests.

Restricted and repetitive behaviour: Inflexibility of behaviour, difficulty coping with change or other restricted and repetitive behaviours occur frequently enough to be obvious to the casual observer and interfere with functioning in a variety of contexts. Significant distress and difficulty changing focus or action.

NDIS eligibility: Level 2 ASD is included in NDIS Condition List A. NDIS disability eligibility is generally established on the basis of a confirmed diagnosis. Functional evidence is still required to determine the level and nature of support funded in the plan.

Level 3: Requiring Very Substantial Support

Social communication: Severe deficits in verbal and non-verbal social communication skills cause severe impairment in functioning. Very limited initiation of social interactions and minimal response to social approaches from others. Communication may be limited to a few words or phrases, or entirely non-verbal. The person primarily communicates to meet immediate needs. Verbal communication, where present, is often not used for social reciprocity.

Restricted and repetitive behaviour: Inflexibility of behaviour, extreme difficulty coping with change or other restricted and repetitive behaviours markedly interfere with functioning in all spheres. Great distress and difficulty changing focus or action. Behaviours of concern including physical aggression, self-injurious behaviour and elopement are common at this level and can present significant safety risks requiring continuous supervision.

NDIS eligibility: Level 3 ASD is included in NDIS Condition List A. NDIS disability eligibility is generally established on the basis of a confirmed diagnosis. Comprehensive functional evidence is required to ensure the plan reflects the full extent of the person’s support needs, including 24-hour care requirements where clinically indicated.

Severe or profound autism: community language and what it means clinically

In the community, Level 3 ASD is sometimes referred to as severe autism, profound autism or autism with high support needs. This informal terminology is used by families, carers, community organisations including Autism Australia and disability service providers to describe people with ASD who require very substantial ongoing support. The terminology is not part of the DSM-5 diagnostic framework, which uses only the three numbered levels described above.

Clinically, people with Level 3 ASD who are described as having severe or profound autism typically present with some or all of the following: absent or very limited functional speech, significant sensory processing differences that affect daily functioning across all environments, extreme difficulty with routine changes and transitions, significant behaviours of concern including physical aggression toward others, self-injurious behaviour and elopement risk, an inability to safely access the community without continuous supervision and, in many cases, a requirement for 24-hour care.

Where a person with Level 3 ASD also has a co-occurring intellectual disability, the functional impact is compounded significantly. Intellectual disability ranges from mild through moderate and severe to profound. A person with Level 3 ASD and profound intellectual disability has support needs that are among the most complex in the NDIS population. This combination must be specifically documented in the Functional Capacity Assessment, as it directly determines the level of support required, the nature of the assessment approach and the clinical recommendations made across all NDIS domains.

How the diagnostic levels interact with NDIS eligibility

Level 2 and Level 3: List A

A confirmed diagnosis of ASD at Level 2 or Level 3 under DSM-5 criteria is included in NDIS Condition List A. List A conditions are those the NDIA considers almost always likely to meet the disability requirements for access under section 24 of the NDIS Act. For most applicants with a confirmed Level 2 or Level 3 ASD diagnosis, NDIS disability eligibility is likely to be established at the access stage without extensive additional functional evidence being required to establish access.

This does not mean that a Functional Capacity Assessment is unnecessary for Level 2 or Level 3 participants. NDIS eligibility and NDIS plan funding are two different things. Eligibility determines whether a person can access the scheme. Plan funding determines how much support is provided and what it covers. The level of funding in an NDIS plan is determined entirely by the participant’s functional support needs, which are documented through functional evidence. A participant with Level 3 ASD who has not had a comprehensive, current Functional Capacity Assessment is at significant risk of receiving a plan that does not reflect the full extent of their support needs.

Level 1: List B

A confirmed diagnosis of ASD at Level 1 under DSM-5 criteria is included in NDIS Condition List B. List B conditions are those the NDIA considers are permanently present but for which the degree of functional impact is variable across individuals and further assessment is generally required. NDIS eligibility for a person with Level 1 ASD is not automatic. The applicant must demonstrate that their ASD results in substantially reduced functional capacity across one or more of the NDIS functional domains: communication, social interaction, learning, mobility, self care or self management.

Since the October 2024 NDIS legislative reforms, NDIA decision makers have been placing increasing weight on functional evidence in eligibility decisions for people with Level 1 ASD. A Functional Capacity Assessment that documents specific, observed functional impairments and links them clearly to the ASD presentation provides the strongest available evidence for NDIS access and planning decisions under the current legislative framework.

Why the diagnostic level alone does not determine support needs

The ASD severity levels describe the degree of support required at the time of diagnosis in broad terms. They were designed as a communication tool for clinicians, not as a precise measure of daily functional capacity. Two people with the same diagnostic level can have profoundly different functional profiles, different support needs and different daily experiences depending on a range of factors.

• Co-occurring conditions including intellectual disability, anxiety disorders, ADHD, epilepsy and mental health conditions significantly affect functional capacity and support needs independently of the ASD level.
• Masking, the learned strategy of concealing or suppressing autistic traits in social settings to appear more neurotypical, can cause a person’s actual functional needs to be significantly underestimated in brief clinical assessments. Masking is associated with significant fatigue, burnout and mental health difficulties.
• Environmental context affects functional presentation substantially. A person with Level 1 ASD may appear to function well in a structured, familiar, low demand environment but be unable to function independently in an unstructured, novel or sensory demanding environment.
• Functional capacity fluctuates across the day, across environments and across levels of demand. A single cross sectional clinical assessment does not capture this variation.

The NDIS requires functional evidence that documents what a person can and cannot do in their actual daily life, what support they require to perform daily activities safely and independently and how their disability affects participation across different environments and life domains. This is what a Functional Capacity Assessment provides. The diagnostic level is a starting point. The FCA is the clinical foundation.

How ASD affects daily functioning across the three levels

Sensory processing

Sensory processing differences are present across all three ASD levels and represent one of the most functionally significant and most frequently underrepresented aspects of ASD in NDIS documentation. People with ASD may be hypersensitive or hyposensitive to sensory inputs including sound, light, touch, smell, taste, temperature and proprioceptive input. Hypersensitivity to sound can prevent a person from tolerating environments such as shopping centres, public transport, open plan workplaces and school classrooms. Tactile hypersensitivity can make personal care tasks such as showering, having hair washed, wearing certain clothing and toothbrushing extremely distressing. Sensory overload occurs when sensory inputs exceed the person’s capacity to process them and can result in a meltdown or shutdown response that temporarily prevents all purposeful activity and requires significant recovery time.

Executive functioning

Executive functioning refers to the higher order cognitive processes that allow a person to plan, initiate, organise, prioritise, sequence and complete tasks, manage time, regulate emotional responses and sustain effort toward goals. Executive functioning difficulties are present across all ASD levels and are one of the most functionally significant aspects of the condition for independent daily living. Difficulties may include inability to initiate tasks despite knowing they need to be done, significant difficulty managing time resulting in chronic lateness and missed appointments, difficulty sequencing and completing multi-step tasks such as meal preparation, personal care and household management, and poor working memory affecting the ability to follow instructions and retain information from conversations.

Executive functioning difficulties are frequently not apparent in a brief, structured clinical appointment. The person may describe what they intend to do, respond well to direct questions and appear organised in the clinical setting. The actual impact of executive functioning on daily functioning is best captured through direct observation in the home environment and through detailed collateral history from people who support the person across daily life.

Emotional regulation

Emotional regulation difficulties are common across all ASD levels and can significantly affect daily functioning, relationships, community participation and safety. These difficulties include intense emotional responses that are disproportionate to the triggering event, difficulty recovering from distress in a reasonable timeframe, limited ability to use cognitive strategies to manage emotional states and significant distress in response to changes in routine, sensory overload or social misunderstanding.

For children, emotional regulation difficulties often present as meltdowns, which are intense behavioural responses to overwhelming stimulation or demand that involve a loss of behavioural control, and shutdowns, which involve withdrawal, unresponsiveness and inability to communicate or function. The after school restraint collapse is a specific pattern in which children with ASD suppress and manage their emotional and behavioural responses throughout the school day and then experience significant dysregulation at home following school. This pattern is common, clinically important and frequently missed in assessments that only address in-school functioning.

Communication

Communication differences vary significantly across the three ASD levels. At Level 1, the person communicates verbally but may have difficulty with the pragmatic, social and contextual aspects of language: understanding implied meaning, managing the turn taking of conversation, knowing what is relevant to say in a given context and calibrating the appropriate level of detail or formality. At Level 2, verbal communication is more limited and more concrete. The person may communicate effectively about their immediate needs and known topics but struggle significantly with the communication demands of unfamiliar settings, services and social situations. At Level 3, verbal communication may be minimal, restricted to specific phrases or entirely absent. Augmentative and alternative communication strategies may be used or required.

Safety and community access

Safety risks associated with ASD vary considerably across the three levels but are present at all levels. Elopement, the sudden and impulsive departure from a safe environment without awareness of or regard for associated risks including road traffic and water, is a significant safety concern particularly at Levels 2 and 3 and in children. Road safety awareness, vulnerability to exploitation and poor understanding of social dangers are relevant at all levels. For people with Level 1 ASD, vulnerability to financial exploitation, social manipulation and online safety risks may be clinically significant even where the person appears highly capable in structured settings.

Specific behaviours of concern in ASD

Beyond the core features of ASD, a range of behaviours of concern occur across the three levels, particularly at Levels 2 and 3 and in individuals with co-occurring intellectual disability. These behaviours are not deliberate or defiant. They are clinically understood as functional behaviours: they serve a purpose and frequently communicate an unmet sensory need, pain, distress, boredom or an environment that exceeds the person’s capacity to cope. Each must be specifically assessed and documented in the Functional Capacity Assessment because of their direct implications for support ratios, supervision requirements, home environment design and carer wellbeing.

Pica

Pica is the persistent ingestion of non-food items. Items ingested may include dirt, paper, hair, paint, small plastic objects, stones, cloth, and in some cases faeces. Research indicates that approximately 23.2 per cent of children with ASD exhibit pica, rising to approximately 28.1 per cent in children with co-occurring ASD and intellectual disability. This compares with approximately 3.5 per cent in the general child population. Pica in ASD is understood to be associated with sensory seeking behaviour, nutritional deficiencies, gastrointestinal discomfort, anxiety and, in people with limited communication, a possible expression of internal distress that cannot otherwise be communicated.

Pica carries significant medical risks including gastrointestinal obstruction, poisoning from ingestion of toxic substances such as paint or cleaning products, dental damage and serious infection. Where pica is present, the Functional Capacity Assessment must document what items are ingested, the frequency, the associated risks and the level of supervision required to maintain safety. This information directly justifies increased supervision ratios, home environment modifications and safety equipment funding.

Faecal smearing

Faecal smearing, also referred to clinically as scatolia, is the inappropriate handling or spreading of faeces. It occurs more frequently in individuals with ASD who have co-occurring intellectual disability, limited communication and significant sensory processing differences. Research suggests that the majority of children with ASD experience sensory processing differences, and faecal smearing may occur as a sensory seeking behaviour, as a response to gastrointestinal discomfort or pain, as a consequence of incomplete toilet training, or as a form of communication or self-stimulation in individuals who have very limited means of expressing their internal state.

Faecal smearing has a profound impact on family functioning, carer wellbeing and daily routines. It significantly affects the practical management of personal hygiene, the design of the bathroom and toilet environment and the level of active supervision required at all times. Where this behaviour is present, it must be documented in the Functional Capacity Assessment with clinical specificity, including frequency, context, the associated triggers where identifiable and the level of supervision and environmental modification required to manage it safely and with dignity. This documentation directly informs recommendations for accessible bathroom design, appropriate shower and toilet spaces that allow carer assistance, and the support worker time and ratios required for personal care.

Food selectivity and restrictive eating

Food selectivity, the restriction of diet to a narrow range of accepted foods, is one of the most common and most functionally significant feeding issues in ASD. Research indicates a prevalence of between 51 and 89 per cent in children with ASD, substantially higher than in typically developing children. Food selectivity in ASD is driven primarily by sensory hypersensitivity to the texture, smell, temperature, colour and appearance of foods. A child may refuse entire food groups, react with severe distress to new foods being introduced, insist on specific brands and presentations and become completely unable to eat in unfamiliar environments.

Food selectivity can result in nutritional deficiencies including low iron, vitamin D, vitamin B12 and calcium, with direct implications for physical development and health. It significantly affects daily family routines, the ability to access community settings including restaurants and social gatherings, school participation and the carer burden associated with preparing and managing meals. At Levels 2 and 3, the rigidity around food may be extreme and attempts to introduce new foods may trigger significant behavioural responses. The Functional Capacity Assessment must document the functional impact of food selectivity on daily living and the level of support and environmental accommodation required.

Incontinence and toileting difficulties

Incontinence and significant toileting difficulties are common across Level 2 and Level 3 ASD and are one of the most functionally and practically significant challenges for individuals, families and support workers. Toilet training in ASD is frequently delayed well beyond the typical developmental window, and in some individuals with Level 3 ASD and co-occurring intellectual disability, continence may not be achieved at all or may be achieved only partially and unreliably.

Several factors specific to ASD contribute to toileting difficulties. Sensory processing differences affect the person’s ability to accurately sense and interpret the internal body signals that indicate a need to toilet, meaning the person may not recognise the need until they are already incontinent. The toileting process is a complex, multi-step sequence involving recognising the need, communicating it or acting on it independently, undressing, managing the toilet environment, completing the process safely and redressing. For individuals with significant executive functioning difficulties, limited communication and poor body awareness, each stage of this sequence may present a genuine functional barrier. Anxiety around the toilet environment, including sensitivity to the sounds, smells, textures and temperature of bathrooms, is common and can cause complete refusal of the toilet environment.

Bowel dysfunction, including chronic constipation and diarrhoea, is documented at significantly higher rates in individuals with ASD compared to the general population, with some research indicating gastrointestinal symptoms are four times more common in this group. Bowel discomfort and unpredictability directly affect toileting management and the level of support required.

Where incontinence is present at Levels 2 and 3, the Functional Capacity Assessment must document the nature and frequency of incontinence episodes, the associated sensory, communication and functional factors contributing to them, the level of support required for personal care and toileting management and the implications for the design of the bathroom and toilet environment. This documentation is directly relevant to the funding of continence products under the NDIS Core Supports budget, the personal care support hours required, accessible bathroom design including the space required for a carer to safely assist with toileting and showering, and appropriate shower and toilet layout to accommodate both the individual and their support person with dignity.

Other specific behaviours of concern

Additional behaviours of concern that may be present across ASD levels, particularly at Levels 2 and 3, include repetitive self-stimulatory behaviours (stimming) that may escalate to self-injury including head banging against walls or floors, biting of the hands and arms and skin picking; physical aggression toward others including support workers and family members; destruction of property including breaking furniture, windows and household objects; sleep disturbance including chronic difficulty initiating sleep, frequent night waking and complete reversal of day and night sleep patterns; and toileting difficulties including resistance to toilet training, refusal to use the toilet and incontinence beyond the expected developmental age.

Each of these behaviours has direct implications for the level of supervision required, the design of the living environment, the staffing ratio needed for safe support, the carer burden on families and the nature of home modifications and assistive technology that may be required. All clinically significant behaviours of concern must be documented in the Functional Capacity Assessment with specificity regarding their frequency, severity, context and functional implications.

ASD with co-occurring intellectual disability: specific challenges

Intellectual disability co-occurs with ASD in a significant proportion of the ASD population. Research suggests that intellectual disability is present in approximately 40 to 50 per cent of individuals with ASD globally, with higher rates in those diagnosed at earlier ages and in those with Level 2 and Level 3 ASD. The presence of intellectual disability alongside ASD creates a clinical profile that is more complex than either condition alone and that presents specific challenges for assessment, diagnosis, NDIS planning and daily support.

Diagnostic challenges

Under DSM-5, a dual diagnosis of ASD and intellectual disability requires that the social communication deficits observed be below the level expected for the person’s general developmental level, not simply below chronological age norms. This is an important clinical distinction. A child with moderate intellectual disability will have delayed social communication development as part of the intellectual disability itself. The ASD diagnosis requires that the social communication deficit is even further below the level expected given their developmental stage. Getting this diagnostic distinction right is important because it determines the NDIS conditions under which the person is assessed for access and the nature of the functional evidence required.

Compounded functional impact

When ASD and intellectual disability co-occur, the functional consequences are additive and interactive. Intellectual disability affects the person’s capacity to learn, understand, reason, solve problems and manage the demands of daily life. ASD affects the person’s social communication, sensory processing, behavioural flexibility and ability to cope with change. Together, these two conditions create a profile characterised by profound difficulty with adaptive functioning across all domains, significantly increased behaviours of concern, severely limited communication and a need for intensive, highly structured, highly consistent support across all environments and activities.

The interaction between ASD and intellectual disability also affects how the person experiences and responds to their environment in ways that are clinically important for support planning. Sensory difficulties that might be managed independently by a person with ASD who does not have intellectual disability may be entirely unmanageable for a person with both conditions, because the intellectual disability affects the person’s capacity to develop coping strategies, request support or tolerate even brief periods of sensory discomfort without a significant behavioural response.

NDIS documentation requirements

For NDIS participants with co-occurring ASD and intellectual disability, the Functional Capacity Assessment must document both conditions and their interaction. The assessment must clearly establish how the functional impact of the ASD presentation is clinically distinct from the intellectual disability presentation, as the NDIS may fund different supports for each condition and the evidence base for each must be clearly articulated. It must also document the combined functional impact of both conditions on each NDIS domain, as the compounded support needs will typically be significantly greater than what either condition would generate in isolation. For participants with severe or profound intellectual disability co-occurring with Level 3 ASD, the total daily support requirement, including the potential need for 24-hour care, must be specifically and comprehensively documented.

What a Functional Capacity Assessment covers for people with ASD

A Functional Capacity Assessment completed by an experienced Occupational Therapist is the primary mechanism through which the functional impact of ASD is documented in the language the NDIS requires to make access and funding decisions. The assessment is completed in person in the participant’s home and community environment, not in a clinical office setting.

• Assessment of sensory processing differences and their functional impact across home, community and, where relevant, school or work environments, including specific sensory triggers and the functional cost of sensory overload
• Assessment of executive functioning difficulties and their impact on the person’s ability to initiate, plan, organise and complete daily living tasks independently, including personal care, meal preparation, household management, financial management and appointment attendance
• Assessment of communication and the support required to meet daily communication needs across different environments and contexts
• Assessment of emotional regulation and its functional impact on daily activities, safety and community participation, including the pattern of emotional dysregulation across the day and across different settings
• Assessment of masking and the functional cost of concealing ASD traits in social settings, including autistic burnout where clinically relevant
• Assessment of safety, including elopement risk, road safety awareness, vulnerability in the community and the level of supervision required
• Assessment of the functional impact of co-occurring conditions including intellectual disability, anxiety, ADHD and other relevant diagnoses
• For children: assessment of the additional care required of parents and carers beyond ordinary parental responsibility, documenting the nature, frequency, duration and functional impact of disability-specific care provision
• Documentation of functional capacity across different times of day, different environments and different demand levels
• Specific recommendations across each NDIS functional domain grounded in direct observation and clinical reasoning

The 2026 NDIS legislative context

The NDIS Amendment (Getting the NDIS Back on Track No.1) Act 2024, which commenced in October 2024, shifted the NDIS framework toward a greater emphasis on demonstrated functional capacity rather than diagnosis. The Securing the NDIS for Future Generations Bill 2026, introduced to Parliament on 14 May 2026, proposes to formally define substantially reduced functional capacity in legislation for the first time and to strengthen the requirement that NDIS supports must have a direct causal connection to the eligible impairment.

For people with ASD at all diagnostic levels, the direction of NDIS reform is clear: functional evidence that is specific, clinically grounded and directly linked to the ASD presentation is the primary determinant of access and funding outcomes. The diagnostic level is a necessary starting point. It is not sufficient on its own.

For children with ASD under the age of 9, the Thriving Kids program commencing 1 October 2026 is relevant. Children with low to moderate support needs will be directed to Thriving Kids rather than the NDIS. Children with high support needs will remain in the NDIS. The threshold between these two pathways is currently being determined by a Technical Advisory Group. Current, comprehensive functional evidence documenting a child’s support needs is important for families whose child is under 9 and approaching this transition.

Who can refer for a Functional Capacity Assessment?

Referrals are accepted from participants and families, support coordinators, paediatricians, psychologists, GPs, early intervention providers and legal representatives involved in NDIS appeals or Administrative Review Tribunal matters. Sina OT has completed Functional Capacity Assessments for individuals with Autism Spectrum Disorder at all diagnostic levels across the lifespan, from early childhood through to adulthood. All assessments are completed in person in the participant’s home and community environment. Assessments are conducted across Adelaide, Melbourne and Sydney and in regional South Australia. Services are available in English and Farsi (Persian).