This is one of the first questions most people ask once they're seriously considering a tiny home — and the short answer is that "on wheels" doesn't mean "no rules." It means different rules, and they vary by council.
Granny flats sit under a statewide pathway
Victoria has a statewide small second dwelling pathway covering fixed secondary dwellings up to 60 square metres. Meeting the eligibility criteria can mean a planning permit isn't required — but a building permit is still required regardless, covering structural safety, energy performance and compliance with the National Construction Code. Council overlays such as bushfire, flood, heritage or vegetation protection can still trigger extra requirements even within that pathway.
Tiny homes on wheels sit under a different framework
A tiny home built on a trailer and registered as a movable dwelling is treated differently to a fixed granny flat — it isn't assessed under the same secondary dwelling pathway. But that doesn't mean it's unregulated. Councils vary significantly in how they handle moveable dwellings: how long you can live in one, what services it can connect to, and where it can be placed on a property.
The one rule that's actually universal
Check with your specific local council before you buy or place a tiny home on a property. The difference between councils on this exact question can be significant, and it's a five-minute phone call that can save a lot of hassle later.