A BASIX Certificate records the sustainability commitments attached to a proposed residential development in New South Wales. It identifies the project, summarises the assessment results and sets out the water, energy, thermal-performance and materials measures that need to be reflected in the approval documentation and completed during construction.
The Certificate is not a record of the home’s actual future water use or energy bills. It is based on the proposed design and nominated systems. Its commitments describe how the development must be documented and built for the assessed result to remain valid.
The exact format and number of commitments vary according to the project type, assessment pathway and selected design measures. A new dwelling using NatHERS simulation may contain more detailed construction and glazing information than a smaller alteration with a limited assessment scope.
In Brief
What Information Appears on a BASIX Certificate?
A BASIX Certificate generally contains the certificate number and issue date, site and project details, assessment results and a schedule of project-specific commitments. These commitments may cover water fixtures and rainwater reuse, construction and insulation, glazing, thermal-performance documentation, hot water, heating, cooling, ventilation, lighting, renewable energy and other nominated measures. It also indicates which commitments must appear on the DA plans, which must be included in the CC or CDC plans and specifications, and which must be checked before an occupation certificate is issued.
BASIX Report or BASIX Certificate?
The terms BASIX report and BASIX Certificate are often used interchangeably in everyday project discussions. The formal approval document generated after the applicable assessment requirements have been met is the BASIX Certificate.
The Certificate lists the design elements that become sustainability commitments for the development. It is submitted with the relevant development application or complying development certificate documentation and is later used during construction certification and occupation certification.
Supporting assessment information, consultant calculations and NatHERS documentation may also exist, but these should not be confused with the issued BASIX Certificate itself.
BASIX Certificate Sections at a Glance
| Certificate Section | Typical Information |
|---|---|
| Certificate identification | Certificate number, date of issue, certificate version and validity information. |
| Project summary | Project name, address, local government area, lot and plan details, project type, dwelling information and certificate preparer. |
| Assessment results | Water and energy scores, thermal-performance result and materials information where applicable. |
| Water commitments | Fixtures, rainwater tanks, connected roof catchment, reuse connections, landscape measures and other nominated water systems. |
| Thermal performance and materials | Assessment method, NatHERS details where relevant, construction systems, insulation, glazing and reported material selections. |
| Energy commitments | Hot water, heating, cooling, ventilation, lighting, renewable energy and other nominated operational systems. |
| Documentation and inspection indicators | Markers identifying which commitments must be shown on DA plans, CC or CDC plans and specifications, or checked by the certifier. |
1. Certificate Number, Issue Date and Validity
The front page identifies the document as a BASIX Certificate and provides its unique certificate number. This number allows the Certificate to be matched with the project and supporting approval documentation.
The front page may also include:
- the Certificate date of issue
- the BASIX tool or certificate version
- a statement explaining the conditions under which the Certificate is valid
- a requirement to submit it within the applicable validity period
- a note identifying any accompanying NatHERS Assessor Certificate
The issue date should be checked before lodgement. If the Certificate has expired before it is submitted, or if the design has changed materially, the assessment may need to be reviewed and a current Certificate generated.
2. Project and Site Details
A BASIX Certificate identifies the residential development to which the commitments apply. The project information should match the architectural plans and approval application.
Depending on the development, the Certificate may record:
- project name
- street address
- local government area
- lot, section and deposited-plan details
- residential project type
- number of dwellings or bedrooms
- site, roof and floor areas
- garden and landscape areas
- information about an existing dwelling where relevant
- the person or company that prepared the Certificate
Incorrect project details can create a mismatch between the Certificate and the application. The site address, lot details, development type and dwelling information should therefore be checked before issue and again before lodgement.
Important Distinction
The Certificate Records Commitments, Not Measured Performance
The water, energy and thermal results are calculated from the proposed design and selected systems. They are not post-construction measurements of water consumption, electricity use, indoor temperature or household behaviour.
Actual performance can be affected by construction quality, installation, operation, occupancy and climate. The Certificate’s function is to establish the design and construction commitments required for the approved development.
3. BASIX Scores and Assessment Results
The project summary commonly displays the principal BASIX assessment results. These allow the reader to see whether the proposed development has met the applicable requirements before the detailed commitments are reviewed.
Water
Water Score and Target
The Certificate may show the project’s water score beside the applicable target. The score reflects the nominated fixtures, alternative water systems, landscaping and other relevant inputs.
Thermal Performance
Pass Result or Thermal Loads
The summary may record a pass result and, where simulation is used, assessor details, climate-zone information and heating and cooling loads.
Energy
Energy Score and Target
The energy score reflects the nominated hot-water, heating, cooling, ventilation, lighting and renewable-energy measures within the assessment.
Materials
Materials Index Information
For applicable projects, the Certificate may record a materials result associated with the calculation and reporting of embodied emissions from nominated construction materials.
The summary result does not replace the detailed schedule. A project may achieve its assessment targets only because particular systems, products or construction measures have been nominated. Those commitments still need to be documented and delivered.
4. Water Commitments
The water section identifies the measures relied upon to achieve the project’s BASIX water result. The exact commitments depend on the dwelling type, site and information entered during the assessment.
Water commitments may include:
- minimum showerhead efficiency ratings
- toilet-flushing-system ratings
- kitchen and bathroom tap ratings
- rainwater-tank capacity
- the minimum roof catchment connected to the tank
- toilet, laundry or outdoor-tap connections
- alternative water sources
- garden, lawn and low-water-use landscape areas
- swimming-pool or spa measures where relevant
- shared systems for multi-dwelling developments
A rainwater commitment is more detailed than a tank-size note. It may also specify how much roof area must drain to the tank and which fixtures or external uses must be supplied by it.
These requirements need to align with the architectural, landscape and hydraulic documentation. A tank shown on one drawing is not sufficient if its capacity, catchment or connections conflict with the BASIX Certificate.
5. Thermal-Performance Commitments
The thermal-performance section records the design and construction measures used to demonstrate that the dwelling satisfies the applicable heating and cooling requirements.
The content varies according to whether the project uses the BASIX DIY Method, NatHERS Simulation Method, Passive House pathway or another accepted assessment approach.
Thermal-performance commitments may address:
- floor, wall, ceiling and roof construction
- insulation materials and minimum performance
- roof and wall colour or solar absorptance where relevant
- window, glazed-door and skylight areas
- frame materials and glazing types
- glazing performance limits
- shading and external obstructions
- ceiling-fan locations
- NatHERS heating and cooling loads where simulation is used
The Certificate should be read together with the approval drawings and any associated assessor documentation. A thermal-performance result is only meaningful when the modelled construction, glazing and shading are carried through into the final project.
6. Materials and Embodied-Emissions Information
For applicable new residential development, BASIX also records information about construction materials so that embodied emissions can be calculated and reported.
The Certificate may identify the selected floor, wall, roof, ceiling, frame, glazing and insulation systems. It may also include calculated construction areas and a materials result in the project summary.
Materials reporting should not be interpreted as a complete lifecycle assessment of the project. BASIX uses the information required by its Materials Index and assessment framework. A project-specific lifecycle assessment may consider a broader range of products, lifecycle stages and environmental indicators.
Where a nominated construction material changes during documentation or procurement, the BASIX information should be checked before the substitution is accepted.
7. Energy Commitments
The energy section identifies the building systems and measures relied upon to achieve the project’s energy result. These commitments generally concern operational systems rather than the thermal envelope itself.
Depending on the project, the Certificate may nominate:
- hot-water-system type and performance
- heating-system type and efficiency
- cooling-system type and efficiency
- systems serving living areas and bedrooms
- bathroom, kitchen and laundry exhaust ventilation
- ventilation controls and discharge locations
- artificial-lighting efficiency
- natural-lighting measures
- ceiling fans
- photovoltaic-system capacity and installation details
- cooking systems
- outdoor clothes-drying facilities
- shared systems in multi-dwelling development
If the assessment relies on a heat-pump hot-water system, photovoltaic array or particular heating and cooling efficiency, the Certificate may make that selection a binding project commitment. A lower-performing substitution should not be assumed to remain compliant.
8. NatHERS Assessor Details and Supporting Certificate
Where the BASIX Thermal Performance Simulation Method has been used, the BASIX Certificate may identify the NatHERS assessor number, NatHERS Certificate number, climate zone and assessed heating and cooling loads.
The BASIX Certificate and NatHERS Assessor Certificate are related documents, but they are not interchangeable.
BASIX Certificate
Wider Project Commitments
Records the project’s BASIX results and applicable water, energy, thermal-performance and materials commitments.
NatHERS Assessor Certificate
Thermal Simulation Record
Records the accredited thermal assessment, rating details, modelled construction and specifications associated with the NatHERS simulation.
Where the supporting NatHERS Certificate is required, its project details and thermal results should remain consistent with the BASIX Certificate. The endorsed thermal-assessment plans may also need to accompany the approval documentation.
Who can perform a NatHERS assessment? →
9. What Must Be Shown on the Plans?
The commitment schedule includes columns indicating when and where particular requirements must be documented or verified. These indicators are important because not every commitment is handled at the same project stage.
| Indicator | What It Means |
|---|---|
| Show on DA plans | The identified commitment must be shown on the plans accompanying the development application where a DA is being lodged. |
| Show on CC or CDC plans and specifications | The commitment must be carried through into the detailed plans and specifications used for the construction certificate or complying development certificate. |
| Certifier check | The certifying authority must be satisfied that the identified commitment has been fulfilled before the relevant occupation certification can be completed. |
10. What Should Be Checked Before the Certificate Is Used?
The BASIX Certificate should be reviewed as a project document rather than accepted only because it has been generated successfully.
Before lodgement, check that:
- the address and lot details are correct
- the project type and dwelling count match the plans
- floor, roof and landscape areas are current
- rainwater commitments match the hydraulic and architectural information
- construction and insulation match the current specification
- the glazing information reflects the current window schedule
- hot-water, heating, cooling and ventilation selections are acceptable
- any photovoltaic commitment is reflected in the documentation
- the NatHERS and BASIX Certificates are consistent
- all required commitments appear on the correct approval drawings
- the Certificate remains valid for lodgement
This review is particularly important where the design has continued to change after the first assessment. A Certificate prepared from an earlier drawing set may no longer describe the proposed development correctly.
What Is Not Included in a BASIX Certificate?
A BASIX Certificate is an important approval document, but it does not replace the wider project documentation or other professional services.
The Certificate does not generally provide:
- approval of the development application or CDC
- a construction certificate or occupation certificate
- complete architectural, structural or hydraulic design
- confirmation that every planning control has been satisfied
- measured future household water or energy consumption
- a guarantee of indoor comfort or utility-bill savings
- detailed design recommendations for every possible improvement
- a complete lifecycle assessment of embodied carbon
- verification that products have been installed correctly
Consultant advice, NatHERS modelling, architectural documentation, engineering and construction inspections may all sit alongside the BASIX Certificate, but they remain separate project functions.
What Happens If the Design Changes?
Changes to the design do not automatically invalidate every part of the assessment, but relevant changes should be reviewed before amended plans are lodged or substituted products are installed.
A review may be needed when there are changes to:
- floor area or building geometry
- window sizes, locations or performance
- wall, roof or floor construction
- insulation levels
- eaves, awnings or other shading
- rainwater tanks, catchment or reuse connections
- hot-water, heating or cooling systems
- ventilation, lighting or photovoltaic systems
- materials recorded through the assessment
Where a change affects the assessment inputs or certificate commitments, the BASIX and supporting NatHERS documentation may need to be updated so the approval documents remain consistent.
Frequently Asked Questions
BASIX Certificate Contents FAQs
What does a BASIX Certificate show?
It shows the project details, assessment results and the sustainability commitments attached to the proposed development. These may cover water, energy, thermal performance, construction materials, glazing, insulation and nominated building systems.
Is a BASIX report the same as a BASIX Certificate?
The terms are often used informally to describe the same project documentation. The formal document submitted with the approval application is the issued BASIX Certificate. Supporting assessment reports or consultant documents may also exist separately.
Does the Certificate show actual water and energy consumption?
No. BASIX estimates performance from the proposed design and selected systems. The Certificate records assessment results and commitments rather than measured consumption after the home is occupied.
Does a BASIX Certificate include the NatHERS rating?
Where NatHERS simulation is used, the BASIX Certificate may identify the NatHERS assessor, Certificate number, climate zone and heating and cooling results. The separate NatHERS Assessor Certificate may also need to accompany the application.
Are BASIX commitments legally binding?
Once the relevant development consent or complying development certificate is issued, the BASIX commitments form part of the approved development requirements. The project must be documented and constructed consistently with those commitments.
Do all BASIX Certificates contain the same commitments?
No. The content depends on the project type, assessment pathway and selected measures. A new dwelling using thermal simulation can contain different information from an alteration, swimming-pool application or multi-dwelling development.
Who checks that the BASIX commitments have been completed?
Councils and certifiers review BASIX information during the relevant approval stages. Commitments identified for certifier checking must be verified before the applicable occupation certification is completed.
Related Knowledge
Continue Exploring BASIX Documentation
Document note: BASIX Certificate formats and individual commitments vary by project type, assessment pathway and BASIX tool version. The project-specific Certificate and supporting approval documents should always be reviewed together.
Last reviewed: July 2026.
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