What actually goes into your CGT cost base?
Walk through the five cost base elements under s 110-25 ITAA 1997 — acquisition cost, incidental costs, ownership costs, capital improvements and title defence. Tick what you have, and see what likely counts, what likely does not, and the traps that catch people. Confirm with your tax adviser.
Important: The cost base rules in Division 110 are technical, with exclusions and modifications that depend on your specific facts — particularly around amounts you have deducted and how you acquired the asset. This tool gives an indicative read only. Prismi is not a registered tax agent. Consult your accountant or a registered tax adviser before relying on any cost base position.
How did you acquire the asset?
How you acquired the asset determines whether the first element is what you actually paid — or the market value at the time (the market value substitution rule).
Every dollar of cost base is a dollar off the gain.
The cost base is where most CGT calculations are won or lost. Missing a legitimate component overstates the gain and the tax. Including something that does not belong — holding costs on a pre-1991 asset, expenditure already deducted against rental income — understates it, and that is the version the ATO notices.
The rules are also where market value quietly enters the picture. If you acquired the asset from a related party for less than it was worth, or as a gift, the market value substitution rule replaces your first element with the asset's market value at acquisition. Inherited pre-CGT assets take their market value at the date of death. In both cases, the entire cost base rests on a historical valuation.
A number pulled from memory, or a real estate agent's appraisal letter, is not substantiated evidence. An independent retrospective market valuation — with methodology, comparable evidence and a defensible file — is.
Prismi does not provide tax advice or calculate cost bases. We provide the independent market valuation evidence that supports the cost base positions your accountant or tax adviser confirms under the legislation.
Indicative Capital Gain Calculator
Put your cost base to work — see your indicative gain and whether the 50% discount may apply.
Market Value Substitution Checker
Does the market value substitution rule rewrite your first element?
Retrospective Valuation
Substantiated market value as at a historical date — acquisition, death, or transfer.
Get the valuation evidence before you lodge.
Related-party acquisitions, gifts and inherited pre-CGT assets all put a historical market value at the base of the calculation. The valuation file is what protects it if reviewed.
Talk to a valuer