A granny flat arrangement sounds informal — Mum moves into the back yard, or an adult child helps their parents build a self-contained unit, and everyone gets on with life. But in Australian law, a "granny flat interest" is a specific, well-defined legal and financial concept, and getting it wrong can quietly cost a family their Age Pension, their aged care fees, or a large chunk of an inheritance. Here's what it actually involves, and how to set one up properly.
What Counts as a Granny Flat Arrangement
You don't need an actual granny flat for this to apply. A granny flat interest is created whenever an older person transfers money, assets, or the title of their home to a family member — usually an adult child — in exchange for the right to live in a property for the rest of their life. That right to live somewhere is called a life interest or granny flat interest, and it's what Centrelink and the Australian Taxation Office both look at closely.
It can involve a purpose-built secondary dwelling, a renovated part of the family home, or simply an agreement that Mum or Dad will always have a room and a right to live in the main house. The physical arrangement matters less than the legal one underneath it.
Why the Tax Treatment Changed
Since 1 July 2021, eligible granny flat arrangements have been exempt from capital gains tax when they're created, varied, or ended — provided the arrangement is genuinely non-commercial. That generally means no market-rate rent is being charged; contributing to household running costs is fine, but if the arrangement looks like a standard rental, the exemption can be lost. Before this change, families often avoided formal granny flat arrangements altogether because triggering CGT on a transfer of the family home was a real risk — which, ironically, pushed many families into informal verbal deals that caused far bigger problems later.
The Centrelink Side: Deprivation and the Five-Year Rule
This is where most families come unstuck. When an older Australian transfers assets — say, the proceeds of selling their home — to a child in return for a granny flat interest, Centrelink needs to assess whether the value of what was given up matches the value of the right to live there. If the person gave away more than the granny flat interest is officially worth, the excess can be treated as a deprived asset, which reduces Age Pension entitlements for up to five years.
There's a related trap for families entering aged care. If a person needs to leave the granny flat within five years of setting up the arrangement — for example, moving into residential aged care — and that need was reasonably foreseeable when the arrangement was made, Centrelink can treat it as though the interest was never validly created, which affects both pension assessment and how aged care fees are calculated. This is precisely why granny flat arrangements should be documented and reviewed with proper advice before they're entered into, not after a health scare forces the issue.
Why It Needs to Be in Writing
A surprising number of Australian families still run granny flat arrangements on a handshake. That works fine until someone disputes it — a sibling questions why the family home was transferred, a relationship breaks down, or Centrelink asks for evidence the arrangement genuinely exists. Without a written agreement, contract of sale, transfer documents, and bank records showing funds actually moved, there's often nothing to point to.
A properly drafted agreement should set out:
- What was transferred (cash, property, or a share of proceeds) and its value
- The exact right being granted — to live in a specific property for life
- What happens if the older person later needs to move into residential aged care
- Who is responsible for outgoings, maintenance, and day-to-day support
- How the arrangement interacts with the family home if it's later sold
Why a Granny Flat Interest Isn't Part of the Estate
Here's a detail that catches families off guard: a granny flat interest only exists during the older person's lifetime. It's a right to occupy, not an asset they own outright, so it doesn't form part of their estate and can't be left to anyone in their will. What matters for the estate is making sure the arrangement — and the family's understanding of it — is consistent with what the will actually says, particularly when siblings are involved and only one of them has been living with, or caring for, the parent.
This is one of the most common sources of family conflict after a death. One sibling assumes the home (or its value) will be split evenly under the will; another assumes their years of live-in care and financial contribution under a granny flat arrangement entitle them to more. Both positions can be reasonable — the problem is usually that nobody wrote anything down at the time, and by the time it matters, the person who could explain the original intention is no longer around to do it.
Getting the Arrangement to Work With the Rest of Your Plan
A granny flat arrangement should never be set up in isolation from the family's broader estate plan. It needs to be considered alongside the will, any enduring power of attorney, and — where the older person is contributing significant funds — how that gift is treated for pension and aged care purposes. Getting specialist advice before the transfer happens, rather than after, is by far the cheapest way to avoid a dispute or a Centrelink assessment nobody expected.
Once the arrangement is documented, the paperwork itself needs to survive the decades it's likely to be relied on — through solicitor changes, house moves, and eventually a transition into aged care. Storing the granny flat agreement, transfer documents, and related correspondence alongside your will and other estate documents in Custodium Vault means your executor and family can find the original agreement when they need it, rather than searching through decades-old paperwork during an already difficult time. Pairing it with life insurance can also help make sure the arrangement doesn't leave one family member financially exposed if circumstances change unexpectedly. See our plans.
The Bottom Line
Granny flat arrangements can be a genuinely good solution for Australian families — keeping an older parent close, reducing aged care costs, and helping adult children access equity earlier. But the informal version of this arrangement is where the risk lives. Treating it as a proper legal and financial decision, documented in writing and reviewed alongside pension, aged care, and estate planning advice, is what turns a well-meaning family agreement into one that actually holds up.
This article is general information only and does not constitute legal advice. For advice specific to your situation, speak with a qualified Australian estate planning lawyer. Our estate planning team can help you document a granny flat arrangement correctly and make sure it fits with the rest of your family's plan.