The tax implications of subdividing your family home | Damian Collins

In a recent blog I discussed the concept of Capital Gains Tax (CGT) and your main residence.

I’m going to take this one step further now and over the next few blogs look at the tax consequences, in particular CGT, if you decide to subdivide your family

This month, I’m going to focus on subdividing your home and selling the rear block.

Let’s start by confirming that it’s unlikely income tax will be applied to any profit you realise, if when you purchased the property, it was never your intention at the time to subdivide.

If however you purchased it with the express intention to subdivide, then income tax may apply.

Whether CGT applies though is another story and is dependent on a couple of things:

  1. If the home was originally purchased before the introduction of CGT on 20th September 1985, then the two properties (now subdivided) will not be subject to CGT.
    Do remember though that if a house was built on the block after this date, then the house would be considered a separate asset and potentially subject to CGT on sale or transfer.
  2. CGT applies only to the sale or transfer of the property. Subdividing does not in itself create a CGT event.
    Also note that when subdividing, if the original property is jointly owned, both parties will be assumed to have a 50/50 interest in the two new properties.

Here’s an example

Sam and Sally purchased their home together in 1991 with no intention of developing the plot.

In 1999, they decide to subdivide their rear block and continue to own both properties jointly. At this stage, no CGT event has been triggered.

But, if Sam was to take ownership of the block in his name and Sally keep the house in her name only, this would trigger a CGT as they have both disposed of (or transferred) a 50% interest in each block.

The house would be CGT free as at the time it is still their main residence, however the rear block would be subject to CGT. The same CGT implications would arise if they sold to a third party.

The other question that often arises is ‘how is the cost base of the new block determined so the tax man can work out how much capital gain is realised’?

Firstly, the cost base is determined based on the original cost base at the time of purchasing the whole parcel of land.

The original cost is then apportioned fairly across each of the two properties.

This could be apportioned based on an area basis or on a market value basis. The cost of acquisition and subdivision are then added to form the total cost base.

Let’s go back to the previous example to explain.

Sam and Sally paid $200,000 in land value for their home originally and are now subdividing the land to create a vacant rear block of 400sqm, leaving 600sqm at the front where the original home stands.

If apportioning the cost based on area, the rear block accounts for 40% of the total original land, thus 40% or $80,000 of the original purchase price.

If under the market value method, then the current value of both properties would be analysed.

In this case, let’s say the rear block is valued at $300,000 and the front at $700,000, thus the rear block is 30% of the total value and therefore 30% of the original purchase price of $200,000.

This is a very simplistic example but demonstrates most importantly, that the cost base is not the value of the new block at the time of subdivision as many people believe.

As always, I encourage you to seek professional advice from your accountant with regards to your circumstances before undertaking any subdivision.

In a future blog I’ll cover building on the new subdivided land and the various tax implications to consider.


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Damian Collins


Damian is managing director of Momentum Wealth, a Perth based property investment consultancy firm. A successful property investor in his own right, Damian formed Momentum Wealth to assist time poor investors in building their portfolios and applies his many years of experience to help clients accelerate their wealth creation. Visit

'The tax implications of subdividing your family home | Damian Collins' have 5 comments


    July 6, 2015 Aloysius Ting

    What if the front block with the existing building is sold and the newly constructed dwelling at the back is used as primary residence for more than 2 years and subsequently sold? The front lot is CGT free. The new dwelling at the back would be, I understand, partially exempt from CGT. How would this be determined?



    December 29, 2014 Hamish

    Thanks for this interesting and well written article which has excellent illustrations.

    What if Sam had transferred his 50% to Sally first? In Victoria this would not attract stamp duty as consideration is for natural love and affection. But would the cost base of the 50% received by Sally now be half of the fair market value on the date of transfer?

    So if the current FMV is $1m (as per above) then Sally’s cost base would be 50% x $200,000 + 50% x $1,000,000 = $600,000.

    And since Sam is disposing of his 50% interest in the principal place of residence there is no CGT payable?

    Is this correct or am I missing something?



    December 29, 2013 Nicola

    Thank you for your article, I would appreciate a link for the previous article …I cannot locate it using search on this blog.


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