Share CGT with 50% discount.
CGT payable
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Net proceeds after CGT
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Your breakdown
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What actually happens when you sell shares
There is no separate capital gains tax in Australia. When you sell shares or ETF units at a profit, the gain is added to your assessable income for that financial year and taxed at your marginal rate alongside your salary. That single fact catches a lot of new investors off guard, because it means the same parcel of CommBank shares can attract very different tax depending on what else you earned that year. Sell in a year you took unpaid leave and your rate is low; sell in a bumper bonus year and the gain rides on top at 37 or 45 percent. This calculator takes your buy price, your sell price, and the top marginal rate you tell it to use, and shows the tax and what is left of the gain.
The 12-month line that halves your bill
The most valuable rule in the whole system is the CGT discount. Hold an asset for more than 12 months before the sale and individuals get a 50 percent discount: only half the gain is taxable. The clock runs from the day after you acquired the shares to the day of the contract to sell, not the settlement date, and one day short of twelve months means the full gain is assessed. I have watched people lose four-figure sums by selling on day 360 of a holding rather than waiting a fortnight. If you are anywhere near the threshold and have a profit, the wait is almost always worth it.
A $15,000 gain on a top rate of 37 percent
Suppose you bought a parcel for $20,000 and sold it for $35,000 after holding it well past a year, and your marginal rate is 37 percent. The tool shows CGT payable of $2,775 and notes that $7,500 is added to your income. The gain after tax is $12,225.
Untick the held-over-12-months box and the same sale taxes the full $15,000, lifting the bill to $5,550. The discount is worth $2,775 here, exactly half the tax. That gap is the visual below.
Losses, parcels, and the order of operations
Capital losses are useful but fussy. A loss can only offset a capital gain, never your salary or other ordinary income, and unused losses carry forward indefinitely until you have a gain to soak them up. The order matters: apply losses to the gross gain first, then take the 50 percent discount on what remains. Do it the other way and you give away half the value of your loss. This calculator focuses on a single profitable parcel, so if you have realised losses elsewhere, deduct them from your gross gain before you enter the figures here.
A second wrinkle is parcel selection. If you have bought the same share at different prices over time, you choose which parcels you are selling, and the ATO expects you to keep records that identify them. Selling your highest-cost parcels first shrinks the taxable gain, though it also burns through the holdings most likely to qualify for the discount, so weigh both. The expert habit is simple: keep a clean spreadsheet of every buy with its date and brokerage, because the cost base includes brokerage on both the buy and the sell, and reconstructing it years later from messy statements is miserable.
Do reinvested dividends count for CGT?
Yes. Under a dividend reinvestment plan each reinvested dividend buys new shares at that day's price, and each of those tranches has its own acquisition date and cost base. The dividend is taxed as income in the year received, and the new shares start their own 12-month discount clock. People routinely forget this and understate their cost base, paying more CGT than they owe.
When is the CGT actually due?
The tax event is the financial year of the sale contract, and you report it in that year's return. There is no separate CGT bill or instalment for a one-off share sale; it flows through your normal assessment. If the sale is large, set the estimated tax aside immediately, because a big realised gain can also push you into a higher bracket or trigger the Medicare levy surcharge for that year.