Section 4.15 now says “significant likely impacts”: what changes for your DA

Since 15 December 2025, section 4.15(1)(b) of the Environmental Planning and Assessment Act 1979 requires a consent authority to consider the significant likely impacts of a development, rather than all of its likely impacts. The change came from the Planning System Reforms Act 2025. The Department of Planning, Housing and Infrastructure’s practice note on section 4.15 explains that to be significant, an impact must be important, notable, weighty or more than ordinary. It also says mitigation counts, and non-significant impacts should generally not be the basis for refusing a DA. Councils can still impose conditions to manage impacts that are not significant, under new section 4.17(1)(a1). For home owners lodging a DA for a house, extension, granny flat or duplex, the reform rewards a Statement of Environmental Effects that identifies the impacts that genuinely matter and shows how they are managed.

Who this is for: home owners and small builders preparing or waiting on a DA in Sydney or regional NSW, who want to understand how the 2025 change to section 4.15 affects what the council assesses, how objections are weighed and what goes in the Statement of Environmental Effects.

What exactly changed in section 4.15?

The Department’s information sheet on the first commencement of the Planning System Reforms Act 2025 lists the changes that took effect on 15 December 2025:

• the word “significant” was inserted before “likely impacts” in section 4.15(1)(b);
• new sections 4.15(1A) and (1B) allow the Regulation to declare factors that are, or are not, relevant to the assessment under section 4.15(1)(b), (c) and (e), and stop consent authorities from considering factors declared not relevant;
• new section 4.17(1)(a1) allows a condition to be imposed if it relates to a likely impact of the development;
• new section 65A of the EP&A Regulation 2021 declares the impacts of other development, for which consent is not sought in the DA, not to be relevant when assessing significant likely impacts.

The other section 4.15 matters are unchanged in structure: the planning instruments and DCP (section 4.15(1)(a)), the suitability of the site (section 4.15(1)(c)), submissions (section 4.15(1)(d)) and the public interest (section 4.15(1)(e)). The practice note confirms there is no hierarchy among them, and the weight given to each is for the consent authority.

Savings provisions mean DAs and modifications lodged before 15 December 2025 are assessed under the old wording, but only for 12 months. Pending applications not determined within that period are assessed under the new provisions.

What counts as a “significant” impact for a house or duplex?

The practice note gives four principles as a starting point: a significant impact is important, notable, weighty or more than ordinary; mitigation proposed as part of the development is taken into account; significance varies with context and setting; and the more remote an impact, the less significant it is likely to be. It also recommends a proportionate, risk-based approach, combining how severe an impact would be with how likely it is.

Applied to typical residential DAs, the change does not make controls optional. DCP and LEP compliance is still assessed under section 4.15(1)(a). What changes is how impacts beyond the controls are weighed. A practical way to think about it:

How are objections treated now?

Submissions are still a mandatory consideration under section 4.15(1)(d). The practice note says they should be considered with a focus on whether the issues raised relate to impacts that are both likely and significant, and that non-significant impacts should generally not form the basis for refusal. For applicants, that means the response to submissions should sort objections honestly: acknowledge and fix the significant ones, show why the others are minor or managed by conditions. For neighbours, it means objections are most effective when they explain why an impact is significant in context, with evidence, rather than listing every possible concern.

What should a Statement of Environmental Effects do differently?

The practice note says applicants should ensure DA documentation clearly identifies and addresses any significant likely impacts, including mitigation, and that requests for further information should target uncertainties about significant impacts rather than minor matters. In our view a good SEE was already doing that, but the reform makes it explicit. We now structure the impact section of SEEs to:

1. identify the impacts that could be significant for this site and context (overshadowing, privacy, bulk, flooding, trees, traffic, heritage);
2. show the evidence for each: diagrams, specialist reports, compliance tables;
3. describe the mitigation built into the design, because mitigation is part of the significance test;
4. group minor impacts briefly and propose conditions to manage them;
5. respond to the section 4.15(1)(a) controls in full, because compliance with the LEP and DCP is still assessed separately.

What the change does not do

It does not remove the need to comply with development standards, and it does not make DCP non-compliances acceptable because their impact is “not significant”. Development standards still need a Clause 4.6 request to be varied, and DCP departures still need to be justified against the objectives of the control. It also does not stop councils considering minor impacts; the practice note says consent authorities may still consider impacts that are less than significant, using proportionality. And the meaning of “significant” will be shaped by the Land and Environment Court over time, which the Department acknowledges in the practice note.

Definitions

Section 4.15

The section of the EP&A Act listing the matters a consent authority must consider when determining a DA.

Significant likely impact

An impact that is important, notable, weighty or more than ordinary, and has a real chance of occurring, assessed after mitigation.

Proportionate assessment

Matching the depth of assessment to the risk of an impact, an object of the EP&A Act since 15 December 2025.

Section 4.17(1)(a1)

The power to impose a condition relating to any likely impact of a development, even one that is not significant.

Section 65A of the Regulation

The provision declaring the impacts of other development, not sought in the DA, irrelevant to the assessment of significant likely impacts.

Our Statements of Environmental Effects are written to the new section 4.15 test, focusing the council on the impacts that matter and the mitigation in the design, and our RFI responses do the same when a council asks for more. For your next DA anywhere in NSW, request a fee proposal.