Written and reviewed by Mary Benton — Australian financial planner specialising in retirement, practising since 2005. About Mary · How we source our figures

Estate Planning & Fairness for Granny Flat Arrangements | Retirement Calculators

Estate Planning & Fairness

When one child receives a significant benefit through a granny flat arrangement, the other children may feel—rightly or wrongly—that they're missing out. Without proper estate planning, this can lead to resentment, disputes, and even legal challenges after your death.

This guide covers strategies for keeping your estate fair, having difficult conversations with your family, and documenting your intentions clearly.

The Fairness Challenge

Consider this common scenario: You have three children—Sarah, Michael, and James. You sell your home for $600,000 and contribute $300,000 to Sarah for a granny flat interest at her property. You keep $300,000 in other assets.

When you pass away, what happens?

Without Estate Planning

Your remaining $300,000 is split equally between three children

Sarah receives

$400,000

$300,000 granny flat + $100,000 inheritance

Michael receives

$100,000

Equal share of remaining assets

James receives

$100,000

Equal share of remaining assets

Result: Sarah receives 4× what her siblings receive. Michael and James may feel this is unfair and could challenge the will or contest the granny flat arrangement.

With Estate Equalisation

Will accounts for the granny flat contribution

Sarah receives

$300,000

Already received via granny flat

Michael receives

$150,000

Half of remaining $300,000

James receives

$150,000

Half of remaining $300,000

Result: Each child receives approximately $200,000 in total value (Sarah's $300,000 is considered an "advance" on her inheritance). While not perfectly equal, it's much fairer.

⚠️ The Legal Reality: In most Australian states, children can challenge a will if they believe they haven't received adequate provision. Even if your will is clear, a disgruntled child may be able to claim more through a "family provision" or "testator's family maintenance" claim. Proper documentation and family communication reduces this risk.

Estate Equalisation Strategies

There are several ways to address the fairness issue. The right approach depends on your assets, your family dynamics, and your wishes.

Most Common

Adjust Inheritance Shares

Reduce the granny flat beneficiary's share of your remaining estate to account for what they've already received.

✅ Advantages

Simple to implement in will
Flexible if circumstances change
No immediate tax implications

❌ Considerations

Requires sufficient other assets
May not achieve perfect equality
Asset values change over time

Life Insurance

Take out a life insurance policy with the other children as beneficiaries, sized to equalise the estate.

✅ Advantages

Creates additional assets
Proceeds paid quickly
Outside the estate (harder to challenge)

❌ Considerations

Premiums can be expensive at older ages
May be difficult to obtain if health issues
Ongoing cost commitment

Documented Gift with Acknowledgment

Treat the granny flat contribution as a documented gift, with all children acknowledging it counts toward Sarah's inheritance.

✅ Advantages

Creates clear documentation
All parties sign and agree
Reduces chance of disputes

❌ Considerations

Requires cooperation from all children
May trigger Centrelink gifting rules
Doesn't prevent legal challenges

Equal Split Regardless

Leave your remaining estate equally to all children, treating the granny flat contribution as a separate arrangement.

✅ Advantages

Simplest approach
Recognises hosting child's contribution
May be appropriate if other children received help earlier

❌ Considerations

Creates significant inequality
May cause resentment
Other children may challenge the will

Calculating Fair Shares

The arithmetic of estate equalisation can get complex. Here's a framework:

The "Hotchpot" Approach

This traditional approach treats the granny flat contribution as an advance on inheritance:

Calculate notional estate: Add the granny flat contribution back to your remaining assets
Divide equally: Calculate each child's "fair share" of the notional estate
Adjust for advances: Reduce the hosting child's share by what they've already received

Hotchpot Example

Three children, $300,000 granny flat, $300,000 remaining assets

Step	Calculation	Amount
Notional estate	$300,000 (granny flat) + $300,000 (remaining)	$600,000
Equal share per child	$600,000 ÷ 3 children	$200,000
Sarah's inheritance share	$200,000 - $300,000 (already received)	$0*
Michael's inheritance share	$200,000 (no advance)	$200,000
James's inheritance share	$200,000 (no advance)	$200,000
Remaining estate distributed		$400,000**

*Sarah received more than her "fair share" upfront, so she gets nothing from the remaining estate.
**This exceeds the $300,000 remaining—you'd need to scale back or accept some inequality.

💡 When the Numbers Don't Work: If the granny flat contribution is larger than one child's "fair share," perfect equality isn't possible from remaining assets alone. Options include: accepting some inequality, using life insurance, or having the hosting child agree to pay back some amount to the estate.

What to Include in Your Will

Your will should clearly document your intentions. Consider including:

1. Statement of Intent

Explain why you're distributing assets the way you are. Courts give weight to documented reasoning.

2. Acknowledgment of Prior Benefits

List any significant gifts or benefits each child has received, including the granny flat contribution.

3. Adjusted Shares

Specify exactly how the remaining estate should be divided, with clear reference to prior benefits.

4. Backup Provisions

What happens if assets change significantly? What if the hosting child predeceases you?

✅ Best Practice: Have your will drafted by a solicitor experienced in estate planning, and review it whenever circumstances change significantly. A properly drafted will is much harder to challenge than a DIY version.

Having the Conversation

The most important protection against inheritance disputes is open communication with all your children—before you commit to the granny flat arrangement.

Conversation Starters

"We're thinking about moving in with [Sarah], and I want to make sure you all understand how this affects our estate planning..."

"We want to be fair to all of you. Here's how we're thinking about balancing the granny flat contribution with your inheritances..."

"I know this might be uncomfortable to discuss, but I'd rather we talk about it now than have disagreements after I'm gone..."

"Do you have any concerns about this arrangement? I want to hear them now so we can address them properly..."

For detailed guidance on these conversations, see our Family Conversation Scripts.

Documenting Everything

Even with a proper will, additional documentation strengthens your position:

Family meeting notes: Keep written records of discussions with all children
Signed acknowledgments: Have all children sign a document acknowledging the arrangement and its estate planning implications
Valuation evidence: Document the value of the granny flat contribution with independent valuations
Reasoning statement: Write a separate document explaining your thinking (can be kept with your will)

⚠️ Keep Originals Safe: Store original signed documents with your solicitor or in a safe place that your executor can access. Keep copies for yourself and consider giving copies to all children so there are no surprises.

What the Hosting Child Should Know

If you're the child hosting the granny flat arrangement, be aware:

Your siblings may resent the arrangement, even if they don't say so now
You may face legal challenges to the will or the granny flat arrangement after your parent's death
Having clear documentation protects you as much as it protects your siblings
Consider whether you're comfortable with a reduced inheritance share in exchange for the arrangement

← Legal Protection Guide Next: Exit Strategies →

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Last reviewed: 26 July 2026