Section 4.55 modification (NSW)

A Section 4.55 modification is the NSW EP&A Act 1979 s.4.55 process for modifying an existing development consent. Once a Development Application (DA) is approved, any subsequent change to the approved design, conditions, or scope requires a formal modification: you can’t just build something different and have the OC catch up. There are three classes (4.55(1), 4.55(1A), 4.55(2)) corresponding to minor error correction, minimal environmental impact, and substantial modifications. The classification determines the assessment pathway and timeline. Section 4.55 modifications are a common cause of OC delays in NSW residential work: the builder discovers as-built differs from the approved drawings during the OC inspection, and the modification has to be lodged and approved before the OC issues. Verified per EP&A Act 1979 (NSW) s.4.55 (2026-05-23).

The three classes:

Class	Trigger	Process
4.55(1)	Minor error, mis-description, or correction	Council officer decision; no public notice; 14 BD typical
4.55(1A)	Minimal environmental impact	Council officer decision; sometimes public notice; 14-30 BD typical
4.55(2)	Substantial modification (changes the nature of the consent)	Full merit assessment; public notice; 3-6 months

4.55(1): minor error correction:

This is the simplest pathway. The applicant identifies a clerical or minor error in the original consent:

Example	What 4.55(1) fixes
Lot description typo in consent	Correction
Address misspelled	Correction
Approved plan version mismatch	Aligns the right plan version
Reference to a missing schedule	Correction
Calculation error in fee or condition	Correction

Council issues an amended consent without further assessment. Typical 14 business days.

4.55(1A): minimal environmental impact:

The proposal modifies the development but with minimal environmental impact. The council must be satisfied that:

• The modified development is substantially the same as that originally approved.
• The environmental impact is minimal.
• Any submissions previously made don’t apply differently.

Example	Why 4.55(1A) is appropriate
Repositioning a window 200mm to allow a built-in wardrobe	Minimal change
Internal layout reconfiguration without structural change	Minimal
Substituting a Colorbond colour for a similar one	Minimal
Adding a small awning over a side entry	Minimal
Minor changes to landscape design	Minimal

Council can require public notification at 4.55(1A) but often doesn’t for small changes. Typical 14-30 business days.

4.55(2): substantial modification:

The proposal substantially modifies the original consent. The council must reassess the proposal on its merits:

Example	Why 4.55(2) is required
New floor or storey added	Significant scale change
Increase in dwelling floor area > 10%	Significant scale change
Change of use (e.g. dwelling to dual occupancy)	Substantial
Significant change to setbacks	Substantial
Heritage element changed	Substantial
Increase in number of bedrooms or dwellings	Substantial
Movement of building envelope > 1 metre	Substantial

A 4.55(2) is functionally a fresh DA: public notification, full merit assessment, conditions, the works. Typical 3-6 months. Cost: $1,500-$5,000 in council fees plus modification documentation.

The OC connection:

The most common 4.55 trigger on residential work is at the OC inspection, when the certifier discovers as-built differs from the approved plans:

As-built deviation	Likely 4.55 class
Window slightly relocated	4.55(1A) typically
Wall position 50-100mm off	4.55(1A)
Garage finish changed colour	4.55(1A)
Roof pitch changed > 2 degrees	4.55(1A) or 4.55(2)
Driveway moved 1+ metres	4.55(2) likely
New dormer added	4.55(2)
Bedroom converted to bathroom	4.55(1A) typically; 4.55(2) if a habitable room count changes
Building footprint enlarged	4.55(2)

The certifier refuses to issue the OC until the modification is lodged and approved. This is the most common cause of OC delays in NSW residential work.

Builder’s pre-OC checklist (to avoid 4.55 surprise):

1. As-built survey before booking the OC inspection.
2. Compare against approved DA drawings systematically.
3. List any deviations with photographs.
4. Lodge 4.55(1A) or (2) as appropriate before the OC application.
5. Approval received before the OC inspection.

Cost and timeline:

Class	Council fee (typical)	Decision time	Builder cost (documentation, fees)
4.55(1)	$0-$500	7-14 BD	$0-$500
4.55(1A)	$500-$1,500	14-30 BD	$500-$2,500
4.55(2)	$1,500-$5,000	3-6 months	$2,000-$10,000+

Common defects:

Defect	Consequence
As-built deviates from approved without 4.55 lodgement	Certifier refuses OC
Misclassified 4.55(1A) when 4.55(2) was required	Council reclassifies; redesign required
Modification documentation insufficient	Council requires additional info; delay
Modification rejected	Either revert to approved plan or rebuild to comply
Builder ignores deviations hoping certifier won’t notice	Discovery at OC inspection; redo more expensive

Cross-state equivalents:

State	Equivalent modification process
NSW	s.4.55 modification (this)
VIC	Amendment to planning permit under PE Act 1987
QLD	Change to development approval under Planning Act 2016
SA	Amendment to planning consent under PDI Act 2016
WA	Amendment to development approval under planning scheme
TAS	Amendment to permit under LUPAA 1993

Builder takeaway:

• Document the project as-built regularly, not at OC; catch deviations early.
• A 4.55(1A) at month 3 is much faster than a 4.55(2) at month 12.
• Engage an architect/town planner for 4.55(2) modifications; substantive justification is required.
• Pre-OC inspection compare against approved drawings; this is the single biggest OC time-saver.

Also known as: s.4.55 modification; s.4.55 amendment; DA modification; consent modification; section 96 modification (old terminology, pre-2018 reform).

Category: Approvals & DA.

Related

• Conditions of consent
• Merit assessment (DA, NSW)
• Occupation Certificate (OC)

See also

• DA process (NSW)

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Last updated: 2026-05-23. Verified: 2026-05-23. Quarterly review for currency.