Australia doesn't have a separate capital gains tax rate. Instead, the taxable portion of your capital gain is simply added to your other income for the year and taxed at your ordinary marginal income tax rate. The main special rule is the 50% CGT discount for assets held longer than 12 months.
If you're an Australian resident individual and you held the asset for more than 12 months before selling, only 50% of the capital gain is included in your assessable income. Assets sold within 12 months of purchase get no discount at all — the full gain is taxable, which is a significant incentive to hold investments for at least a year before selling where possible.
With the 50% discount applied, only $10,000 of the gain is taxable. Added to $80,000 of other income, this pushes total taxable income to $90,000. The extra $10,000 falls entirely within the 30% bracket ($45,001–$135,000), so it generates roughly $3,000 in additional tax — an effective rate of just 15% on the full $20,000 gain.
Because your capital gain stacks on top of your other income, realizing a large gain in a high-income year can push a meaningful portion of that gain into a higher bracket than it would face in a lower-income year. Some investors deliberately time asset sales for years when their other income is lower — for example, after retiring or during a career break — to reduce the marginal rate applied to the gain.
If you sell your main residence, the gain is usually completely exempt from CGT under the main residence exemption, provided the property was your home for the entire period of ownership and wasn't used to produce income (such as being rented out or used for a home business) during that time.
If you have capital losses — from the same year or carried forward from previous years — they reduce your capital gain before the 50% discount is applied, not after. If your losses exceed your gains for the year, the excess carries forward indefinitely to offset future capital gains, but cannot be used to reduce your salary or other ordinary income.