How to Calculate a Fair Buyout When a Co-Owner Wants Out

At some point in many co-ownerships, one owner wants to exit and the other wants to buy them out. The question — what's a fair price? — sounds simple and almost never is. Done casually, it breeds resentment. Done properly, it's just arithmetic. Here's the method.

Start with equity, not value

The most common mistake is calculating the buyout from the property's value. The right starting point is equity — what's actually owned after debt.

Equity = current property value − outstanding mortgage − any government equity share

If a scheme like Help to Buy or the Victorian Homebuyer Fund holds an equity share, settle that off the top first, because the government participates in the gain.

Example. A $760,000 property with a $468,000 loan and no government share has $292,000 of equity to divide between the owners — not $760,000.

Step 1: Get a current valuation

Agree on how value is determined. Options, roughly in order of rigour:

• An independent valuation from a licensed valuer (most defensible)
• A real-estate appraisal (free, but less rigorous)
• An indicative estimate from market data as a starting point for discussion

A good co-ownership agreement names the method in advance so no one argues about it at the worst possible time.

Step 2: Split the equity fairly

Now divide that equity between owners. There are three common methods.

Method 1: By legal title share

Split equity strictly by the percentages on title (e.g. 60/40). Simple and clean — appropriate when contributions have always matched the title split.

Method 2: By contribution

Split equity according to what each owner actually put in — deposits, their share of principal repaid, and capital improvements. This is fairer when the mortgage was paid unequally.

Method 3: Hybrid

Use the title share as the base, then adjust for differences in contributions. Many co-ownership agreements land here because it balances the legal position with real-world fairness.

The right method is whichever your co-ownership agreement specifies. If it doesn't specify one, that's a gap to fix — see how to buy property with a friend or partner.

Step 3: Account for the hidden costs

This is where back-of-the-envelope figures go wrong. A buyout is a real transaction with real costs:

• Transfer (stamp) duty on the share being transferred — payable in most states, though concessions can apply.
• Capital gains tax for the exiting owner if the property isn't their main residence (an investment, for example). The CGT discount may apply if they've held their share for more than 12 months.
• Fixed-rate break costs if the loan is being refinanced during a fixed term.
• Valuation and legal fees.

These can move the net figure by tens of thousands of dollars, and they're easy to forget. The agreement should also say who bears which cost — commonly the buyer pays transfer duty and the exiting owner pays their own CGT.

A worked example

Two owners hold a property 60/40 as tenants in common.

• Current value: $760,000
• Outstanding loan: $468,000
• Equity: $292,000

The 40% owner is exiting. Under a contribution-weighted method that reflects they paid only 30% of the mortgage, their fair share of equity comes out below a naive 40% — say roughly $110,000 rather than $116,800. The buyer then funds that amount (often by refinancing), and the exiting owner pays any CGT on their gain while the buyer covers transfer duty on the transferred 40% share. The exact figures depend on your numbers and state — which is precisely why a tool helps.

Why this is worth getting right

A fair, transparent buyout figure protects the relationship as much as the money. When both owners can see how the number was reached — equity, contribution history, costs — there's nothing to argue about. When it's a guess, there's nothing but argument.

Let Propact calculate it for you

Propact's buyout estimator does exactly this: it takes your valuation, nets off the mortgage and any government share, splits the equity by your chosen method, and itemises the costs — stamp duty, CGT, break costs and valuation — to show the net figure the exiting owner walks away with and the cash the buyer needs.

Try it on the demo to see the equity picture, or create a free account to run it on your own property.

---

This article is general information, not legal, financial or tax advice. Capital gains tax and stamp duty outcomes depend on your circumstances and state — confirm with a licensed professional.