Understanding substantial commencement: Insights from TCT v Mary Ann’s Island

A planning permit must be substantially commenced within two years from the date it came into effect, unless an extension is granted. If substantial commencement is not achieved within this timeframe, the planning permit lapses.

Understanding what constitutes substantial commencement is essential, as it determines whether a planning permit can continue to be relied upon where the development has not been completed after the time to substantially commence the permit has passed.

There has been little consideration of the concept of substantial commencement by the Tasmanian courts. However, the recent Supreme Court decision in Tasmanian Conservation Trust Inv v Mary Ann’s Island Pty Ltd [2026] TASSC 1 (TCT v Mary Ann’s Island) provides some guiding principles on what is required to achieve substantial commencement.

Background on TCT v Mary Ann’s Island

The Tasmanian Conservation Trust (TCT) challenged the validity of a planning permit granted to Mary Ann’s Island Pty Ltd for an 18-hole links style golf course and associated infrastructure at Arm End, Opossum Bay.

TCT argued that the permit had lapsed because substantial commencement was not achieved by 1 October 2022, being the date the permit was required to be substantially commenced.

As at that date, no construction of the golf course or related infrastructure had begun. The only works undertaken were weed eradication activities, including the preparation and implementation of a weed eradication plan.

The Supreme Court’s Decision

The Supreme Court held that assessing substantial commencement involves answering two key questions:

• Was the work undertaken a necessary step in, or part of, the development?
• If so, was the work undertaken sufficient to amount to a substantial commencement of the development?

The Court emphasised that both questions must be answered by reference to the factual and circumstantial context of the case.

It was held that substantial commencement had been achieved in this case because the weed eradication work undertaken:

• was a necessary and intrinsic component of the development; and
• was significant, effective, and involved considerable cost, making it sufficient to constitute substantial commencement.

Accordingly, it was held that the planning permit remains valid because substantial commencement has occurred within the required timeframe.

Key takeaways

The following key takeaways can be drawn from TCT v Mary Ann’s Island when assessing whether substantial commencement has been achieved:

• It should be considered whether the work undertaken is a necessary step in, or part of, the development.
• The assessment of whether the commencement is substantial is a question of degree.
• It is relevant that the works constitute a step in the overall project to which the proponent has already committed or is prepared to commit considerable resources.

Importantly, determining whether a development has been substantially commenced will always be fact specific. While weed eradication works were sufficient in this case, that does not mean similar works will demonstrate substantial commencement in every project.

If you are unsure whether your project has been substantially commenced, or if you are approaching a deadline to achieve substantial commencement, seeking advice early can help protect your development rights.