If you sold shares, ETFs or crypto during the 2025–26 financial year, the ATO expects you to report the capital gain or loss in the tax return you're lodging right now. And if you're like most Australian investors, juggling a CommSec account, a Stake account, maybe some Raiz and a bit of crypto, working out that number means digging through contract notes across three or four platforms that don't talk to each other.
The maths itself isn't complicated. The record-keeping is. This guide walks through how CGT on shares actually works, step by step, using the same logic the ATO applies.
Capital gains tax isn't a separate tax. It's part of your income tax. A "CGT event" happens when you dispose of an asset: selling shares, swapping one crypto token for another, or transferring shares to someone else. Simply holding shares that have gone up in value triggers nothing; unrealised gains aren't taxed.
Your cost base is what the parcel of shares really cost you, which is more than the purchase price. For a typical share investor it includes the amount you paid, brokerage on the purchase and the sale, and certain incidental costs of acquiring or disposing.
For US shares, everything is converted to Australian dollars at the exchange rate on the relevant dates: the purchase-date rate for the cost base and the sale-date rate for the proceeds. You can have an AUD capital gain on a US position that fell in USD terms purely from currency movement.
Capital gain = capital proceeds − cost base, calculated parcel by parcel. This is where spreadsheets start to wobble. If you bought BHP three times over two years and sold half your position, which shares did you sell? The ATO lets you choose the specific parcels, as long as your records support it. That choice matters, because selecting parcels held longer than 12 months can qualify the gain for the 50% discount.
Losses (this year's or carried forward) are offset against gains before any discount is applied. That ordering is set by law and works in your favour. Capital losses can only offset capital gains, not salary or other income, and unused losses carry forward indefinitely if you've recorded them.
Held a parcel for more than 12 months? Only half the remaining gain is taxable. The 12 months runs acquisition to disposal, parcel by parcel. Sell a position built from parcels bought 14 and 9 months ago, and one part of the sale gets the discount while the other doesn't.
There's no separate "CGT rate" in Australia. Your net capital gain is added to assessable income and taxed at your marginal rate. Dividends and franking credits are a separate part of your return (income, not capital gains) but come from the same statements, so most people reconcile both at once.
PortWorth pulls CommSec, Stake, IBKR, Raiz, Vanguard and crypto into one place, keeps parcel-level records automatically, and produces a per-financial-year CGT report with the discount and losses already worked through.
Explore PortWorthNo. CGT applies when a CGT event occurs, typically a disposal. Unrealised paper gains aren't taxed.
No. Unlike some countries, Australia has no annual CGT exemption for shares. Every net gain is assessable.
Contract notes for every buy and sell, DRP statements, and corporate action records. Generally for at least five years after the relevant CGT event.
Companies don't get the discount. Complying super funds get a one-third discount rather than 50%.