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Modifications to the cost base and reduced cost base

Last updated 24 May 2020

In some cases, the general rules for calculating the cost base and reduced cost base have to be modified. For example, you substitute the market value for the first element of the cost base and reduced cost base if:

  • you did not incur expenditure to acquire the asset
  • some or all of the expenditure you incurred cannot be valued, or
  • you did not deal at arm's length with the previous owner in acquiring the asset.

This is known as the market value substitution rule for cost base and reduced cost base.

There are exceptions to the market value substitution rule. One exception is where shares in a company, or units in a unit trust, are issued or allotted to you but you did not pay anything for them.

You do not include expenditure you subsequently recoup - such as an insurance pay-out you receive or an amount paid for by someone else - in the cost base and reduced cost of a CGT asset unless you include the recouped amount in your assessable income.

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Example: Recouped expenditure

John bought a building in 2000 for $200,000 and incurred $10,000 in legal costs associated with the purchase. As part of a settlement, the vendor agreed to pay $4,000 of the legal costs. John did not claim as a tax deduction any part of the $6,000 he paid in legal costs.

He later sells the building. As he received reimbursement of $4,000 of the legal costs, in working out his capital gain, he includes only the $6,000 he incurred in the cost base.

End of example

If you acquire a CGT asset and only part of the expenditure relates to the acquisition of the CGT asset, you can only include that part of the expenditure that is reasonably attributable to the acquisition of the asset in its cost base and reduced cost base.

Apportionment is also required if you incur expenditure and only part of that expenditure relates to another element of the cost base and reduced cost base.

Similarly, if a CGT event happens only to part of your CGT asset, you generally apportion the asset's cost base and reduced cost base to work out the capital gain or capital loss from the CGT event.

Consolidated groups

The rules that apply to members of a consolidated group modify the application of the CGT rules.

For more information about the consolidation rules, visit our website or for technical enquiries, phone the Tax Reform Infoline on 13 24 78.

General value shifting regime

Value shifting generally occurs when a dealing or transaction between two parties is not at market value and results in the value of one asset decreasing and (usually) the value of another asset increasing.

The general value shifting regime (GVSR) rules apply to:

  • value shifts that arise because interests in a company or trust are issued or bought back at other than market value, or because their rights are varied so that the value of some interests increases while the value of others decreases (direct value shifts on interests)
  • value shifts that arise because two entities under the same control or ownership conduct dealings or transactions that are neither at market value nor arm's length, so that the value of interests in one entity decreases while (usually) the value of interests in the other entity increases (indirect value shifting), and
  • value shifts that arise from the creation of a right over a non-depreciating asset in favour of an associate for less than market value (direct value shifts by creating rights).

The rules on direct value shifts on interests target only equity or loan interests held by an individual or entity that controls the company or trust, the controller's associates and, if the company or trust is closely held, any active participants in the arrangement.

The indirect value shifting rules target only equity or loan interests held by an individual or entity that controls the two entities conducting the dealing or transaction and the controller's associates. But if the two entities are closely held, the rules also target equity or loan interests held by two or more common owners of those entities, the common owner's associates and any active participants in the arrangement.

There are also exclusions and safe harbours that limit the operation of the rules.

If the rules apply, you may need to:

  • adjust the cost base and reduced cost base of equity and loan interests affected by the value shift, or
  • adjust a realised loss or gain on the disposal of the relevant assets.

In some cases, there may also be an immediate capital gain.

For more information on whether the GVSR rules apply to you, see General value shifting regime – who it affects. For detailed information on the operation of the rules, see General value shifting regime.

Other special rules

There are other rules that may affect the cost base and reduced cost base of an asset. For example, they are calculated differently:

  • if the asset is your main residence and you use it to produce income for the first time after 20 August 1996 (see chapter 6)
  • if you receive the asset as a beneficiary or as the legal personal representative of a deceased estate (see chapter 9)
  • for bonus shares or units, rights and options and convertible notes (see chapter 5)
  • under a demerger (see chapter 5), and
  • where you have been freed from paying a debt (see Debt forgiveness).

Debt forgiveness

A debt is forgiven if you are freed from the obligation to pay it. Commercial debt forgiveness rules apply to debts forgiven after 27 June 1996. A debt is a commercial debt if part or all of the interest payable on the debt is, or would be, an allowable deduction.

Under the commercial debt forgiveness rules, a forgiven amount may reduce (in the following order) your:

  • prior income year revenue losses
  • unapplied net capital losses from earlier years
  • deductible expenditure, and
  • assets' cost base and reduced cost base.

These rules do not apply if the debt is forgiven:

  • as a result of an action under bankruptcy law
  • in a deceased person's will, or
  • for reasons of natural love and affection.
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Example: Applying a forgiven debt

On 1 July 2006, Josef had available net capital losses of $9,000. On 3 January 2007, he sold shares he had owned for more than 12 months for $20,000. They had a cost base (no indexation) of $7,500. On 1 April 2007, a commercial debt of $15,000 that Josef owed to AZC Pty Ltd was forgiven. Josef had no prior income year revenue losses and no deductible capital expenditure.

Josef must use part of the forgiven commercial debt amount to wipe out his net capital losses and the rest to reduce the cost base of his shares. He works out the amount of net capital gain to include in his assessable income as follows:

Adjust net capital losses:

Available net capital losses


less debt forgiveness adjustment


Adjusted net capital losses


Adjust cost base:

Cost base of shares (no indexation)


less debt forgiveness adjustment


Adjusted cost base (no indexation)


Calculate net capital gain:

Sale of shares


less adjusted cost base (no indexation)


less adjusted net capital losses


Capital gain (eligible for discount)


less discount percentage (50%)


Net capital gain



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