This article is part of the Iris Ethics Knowledge Base; you can find a directory of all articles here.
Overview
An opt-out approach presumes participation unless a person takes action to decline. Potential participants are given information about the research and told how to decline; unless they act on it, their participation, or the use of their data, proceeds. It is a departure from the standard consent principle in NS 2.2, available only where the National Statement's conditions in NS 2.3 are met.
When opt-out is appropriate (NS 2.3.5)
An opt-out approach may be appropriate when it is feasible to contact some or all potential participants, but the project is of such scale and significance that explicit consent is neither practical nor feasible (NS 2.3.5).
Before approving opt-out, the review body must be satisfied that (NS 2.3.6):
- involvement carries no more than low risk to participants (see Assessing risk and benefit (NS 2.1));
- the public interest in the research or evaluation substantially outweighs the public interest in protecting privacy;
- the research or evaluation would likely be compromised unless participation is near-complete, and requiring explicit consent would compromise that participation rate;
- reasonable attempts are made to give all prospective participants plain-language information about what is being collected, why, and how to decline or withdraw;
- a reasonable time is allowed between giving that information and using participants' data, so people have a genuine opportunity to decline before the research or evaluation begins;
- a mechanism exists for prospective participants to get further information and decline to participate;
- data will be managed in accordance with relevant security standards;
- a governance process delineates clear responsibility for the project and for managing the data; and
- the opt-out approach is not prohibited by state, federal or international law.
Opt-out is not a waiver of consent. Participants still need to understand what they are (not) consenting to, and must have a genuine, accessible mechanism to decline; the default simply shifts from "no unless you say yes" to "yes unless you say no." Where a mechanism does not give people a realistic chance to act on the information, the condition at NS 2.3.6(d)-(f) is not met.
The evaluation and QA guidance does not override this chapter
NS 2.3.7 directs readers to the NHMRC's Ethical Considerations in Quality Assurance and Evaluation Activities (2014, or as updated) for guidance on opt-out in activities other than research, such as quality assurance and evaluation, that do not require ethics review at all (NS 2.3.7). This is a narrow carve-out. Most evaluation and quality improvement activities do require ethics review (see Evaluation and quality assurance), and where they do, the NS 2.3.5-2.3.8 conditions govern, not the 2014 QA document.
Design considerations (NS 2.3.8)
When assessing the information and decline mechanism proposed, a review body should consider the sensitivity and risks of the research or evaluation, the potential participant pool, the context in which the research/evaluation and opt-out approach will occur, and whether withdrawal from participation remains feasible once identifiers have been removed from the data (NS 2.3.8). Where data will be de-identified quickly, participants should be told upfront that withdrawal will not be possible after that point.
Privacy law and who can approve opt-out
Opt-out is unlikely to constitute valid consent under Commonwealth privacy legislation for handling sensitive information, including health information (NS 2.3, Introduction). Where it is impracticable to obtain explicit consent and the research or evaluation purpose cannot be met using non-identifiable information, researchers and evaluators must comply with the Guidelines under Section 95 or Section 95A of the Privacy Act 1988 (Cth), as applicable. Only an HREC may grant approval to use an opt-out approach for research or evaluation to which the section 95 or 95A guidelines apply; other review bodies may approve opt-out for research or evaluation to which those guidelines do not apply (NS Chapter 2.3, Introduction). See Lower risk vs full HREC review.
Related resources
This page was last updated on 16 September 2026.
Was this helpful? We'd appreciate your feedback!
This article makes reference to the National Statement on Ethical Conduct in Human Research 2025. It is intended as practical guidance and does not constitute legal advice.
AI Disclosure: Resources in this library were prepared using Large Language Models with input from Iris Ethics staff who guided the scope and design. Subsequent revisions and final versions were developed and approved by Iris Ethics staff.