Disclaimer: This article is for educational purposes only and does not constitute financial or tax advice. Consult a qualified tax professional for advice specific to your situation.
Every Australian who trades shares needs to report capital gains to the ATO. Whether you buy a handful of blue-chip stocks each year or rotate through dozens of positions as a swing trader, understanding Capital Gains Tax (CGT) and tracking it well can save you real money at tax time.
The problem: most traders ignore CGT until they sit down with their tax return in July. By then, reconstructing cost bases, matching parcels, and figuring out which sales qualify for the 50% discount becomes stressful and error-prone.
This guide covers how CGT applies to shares in Australia, how to calculate it, the mistakes to avoid, and the tools that make the process painless.
How Capital Gains Tax Works on Shares in Australia
Capital Gains Tax is not a separate tax. It is part of your income tax. You sell (or "dispose of") shares for more than you paid, the profit is a capital gain, and the ATO requires you to include it in your assessable income for that financial year.
The core rules:
- CGT is triggered on disposal. You owe CGT when you sell, gift, or otherwise dispose of shares. Unrealised gains (shares you still hold that have gone up) are not taxed.
- Capital gains are added to your assessable income. Your net capital gain for the year gets added on top of your salary, business income, and any other income, then taxed at your marginal tax rate.
- Capital losses offset capital gains. If you sell shares at a loss, that capital loss can reduce your capital gains in the same year. If your losses exceed your gains, the net loss carries forward to future years. Capital losses cannot offset ordinary income like your salary.
- The CGT discount reduces the taxable gain by 50%. If you held the shares for at least 12 months before selling, you may be eligible for a 50% discount on the gain. This is one of the most valuable tax concessions available to Australian investors.
- Cost base includes more than the purchase price. Your cost base is not the purchase price alone. It also includes brokerage fees on purchase and any other incidental costs of acquiring the asset.
The CGT Discount Explained
The 50% CGT discount is the single biggest reason to pay attention to your holding periods. Get it right, and you halve the tax you owe on a profitable trade.
Who qualifies?
The discount is available to Australian resident individuals and trusts. It is not available to companies. If you trade through a company structure, you pay tax on the full capital gain at the company tax rate.
The 12-month rule
To qualify, you must have held the asset for at least 12 months before the CGT event (the sale). The 12-month period starts the day after you acquired the shares and ends on the day of disposal.
If you bought shares on 15 January 2025, you need to sell on or after 16 January 2026 to qualify for the discount. Selling on 15 January 2026, 12 months to the day, does not qualify. You need to hold for more than 12 months.
How to apply the discount
The order matters. You must:
- Calculate your capital gain (sale proceeds minus cost base).
- Apply any capital losses against your capital gains.
- Then apply the 50% discount to the remaining gain.
Worked example
You buy 1,000 shares of XYZ.AU at $10.00 per share. Total cost: $10,000. You pay $19.95 brokerage on purchase.
After 14 months, you sell all 1,000 shares at $15.00 per share. Total proceeds: $15,000. You pay $19.95 brokerage on sale.
Cost base: $10,000 + $19.95 (buy brokerage) + $19.95 (sell brokerage) = $10,039.90
Capital gain: $15,000 - $10,039.90 = $4,960.10
Since you held the shares for more than 12 months, you apply the 50% discount:
Discounted gain: $4,960.10 x 50% = $2,480.05
That $2,480.05 is added to your assessable income and taxed at your marginal rate. If your marginal rate is 32.5%, the tax on this gain would be about $806.
Without the discount, the tax would have been about $1,612, so the discount saved you over $800 on a single trade.
How to Calculate Your Cost Base
Your cost base is the total cost of acquiring and disposing of the asset. Getting this right is essential because an understated cost base means you overpay tax, and an overstated cost base means you underreport, which can trigger ATO scrutiny.
What's included in cost base?
- Purchase price. The amount you paid per share multiplied by the number of shares.
- Brokerage on purchase. The commission your broker charged when you bought.
- Brokerage on sale. The commission charged when you sold. This is part of the cost base for CGT purposes.
- Other incidental costs. Stamp duty (if applicable in your state), legal fees, or any other costs tied to the acquisition or disposal.
Handling multiple parcels
If you bought the same stock on different dates at different prices, each purchase is a separate "parcel." You need to identify which parcel you are selling from.
The ATO allows two methods:
- FIFO (First In, First Out). The shares you bought first are treated as the shares you sold first. This is the most common method.
- Specific identification. You choose which specific parcel you are selling from, provided you can identify it. This can be useful for tax optimisation. For example, selling a parcel held for over 12 months to get the CGT discount, even if you also have a more recent parcel.
Whichever method you choose, you must apply it consistently and keep records to support your approach.
Record-keeping requirements
The ATO requires you to keep records of share transactions for at least five years after the CGT event (the sale). This includes:
- Contract notes or trade confirmations
- Purchase date and price
- Sale date and price
- Brokerage and fees
- Any dividend reinvestment plan (DRP) statements
- Records of any corporate actions (stock splits, mergers, demergers)
If you cannot produce these records during an audit, the ATO may use a zero cost base, meaning your entire sale proceeds become a capital gain.
Common Mistakes Australian Traders Make With CGT
These errors come up again and again.
1. Not tracking cost base for each parcel
Many traders track an average cost per share. That is fine for portfolio management, but it is not how CGT works in Australia. You need the cost base for each individual parcel (each separate purchase). Using average cost will produce incorrect tax figures.
2. Forgetting to include brokerage in cost base
Brokerage is a legitimate part of your cost base. On a $10,000 trade with $19.95 brokerage each way, that is $39.90 in fees that reduces your taxable gain. Over dozens of trades per year, this adds up. Do not leave money on the table.
3. Selling before the 12-month mark
This is common with swing traders. You bought a stock 11 months ago, it hit your target, and you sell. You missed the 50% CGT discount. On a $5,000 gain, that is $2,500 in additional assessable income. Check your acquisition dates before selling.
4. Not offsetting capital losses against gains
Some traders let capital losses pile up without realising they can offset gains in the same financial year. If you have $8,000 in gains and $3,000 in losses, your net gain is $5,000. You can also carry forward unused losses to future years, but you must claim them.
5. Confusing trading income with capital gains
If the ATO considers you a "share trader" (someone who trades frequently as a business), your profits may be taxed as ordinary income on revenue account, not as capital gains. You lose access to the 50% CGT discount, but you can claim losses against your other income. The distinction depends on factors like frequency of trading, intent, and whether you run it as a business. If you are unsure, get professional advice.
Tools for Tracking CGT
Manual tracking works when you make a handful of trades per year. Once you trade regularly across multiple stocks or portfolios, manual tracking becomes a liability.
Spreadsheets
The classic approach. You can build a spreadsheet that tracks purchases, sales, cost bases, and holding periods. This works, but it is error-prone for active traders. One missed entry or wrong formula and your tax figures are wrong. Spreadsheets also do not handle corporate actions, stock splits, or DRP parcels automatically.
Broker-provided tax reports
Most Australian brokers provide an annual tax summary. These are useful but limited. They cover trades made through that specific broker and may not calculate the CGT discount correctly if your parcels span multiple brokers.
Dedicated portfolio tracking tools
Purpose-built tools eliminate the manual work and reduce errors. SwingFolio's ATO-ready tax reports calculate CGT for every trade, including:
- Automatic 50% CGT discount applied to eligible positions held over 12 months
- Holding period tracking so you know which trades qualify for the discount before you sell
- Cost base calculations that include brokerage and fees for each parcel
- FIFO parcel matching applied consistently across your trades
- Multi-portfolio support for traders using multiple brokers, with a single consolidated CGT report
You can also use SwingFolio's free CGT calculator to estimate your capital gains on individual trades, and the portfolio analytics dashboard to monitor performance and tax implications across your accounts.
For investors focused on long-term wealth building, the investor tools provide the tracking and reporting features you need to stay on top of your tax obligations year-round.
Frequently Asked Questions
Do I need to report capital gains if I made a loss?
Yes. You must report all capital gains and capital losses in your tax return, even if you had a net loss for the year. Capital losses cannot reduce your other income, but they carry forward to offset future capital gains. If you do not report a loss, you lose the ability to use it later.
How does the 12-month CGT discount work for shares?
If you are an Australian resident individual and you hold shares for more than 12 months before selling at a profit, you apply the 50% CGT discount to the gain. Only half the capital gain is added to your assessable income. You must first subtract any capital losses from your gains, then apply the 50% discount to the remaining amount. The discount does not apply to companies.
Can I use the FIFO method for CGT in Australia?
Yes. The FIFO (First In, First Out) method is accepted by the ATO. Under FIFO, the shares you purchased earliest are treated as the shares you sold first. You can also use the specific identification method if you can identify which parcel of shares you are selling. Whichever method you choose, apply it consistently.
What records do I need to keep for share trading tax?
The ATO requires records of all share purchases and sales for at least five years after the relevant CGT event. This includes trade confirmations, contract notes, brokerage statements, dividend statements (for DRP), and records of corporate actions like stock splits, mergers, or demergers. Digital records are acceptable as long as they are complete and legible.
Conclusion
Tracking CGT throughout the year beats scrambling at tax time. Traders who stay on top of their cost bases, holding periods, and parcel identification pay the right amount of tax, not more, not less.
Track each parcel with its full cost base including brokerage. Know your holding periods so you do not miss the 50% CGT discount. Offset losses against gains within the same financial year and carry forward any unused losses. Use purpose-built tools instead of relying on memory or fragile spreadsheets. Keep records for at least five years after each sale.
SwingFolio's tax reports handle all of this automatically, so tax time becomes a five-minute exercise instead of a five-hour headache.