How the calculation works
- Capital proceeds. What you received for the asset, less selling costs such as brokerage or the agent's commission.
- Cost base. What it cost you: the purchase price plus incidental costs of buying it (brokerage, stamp duty, legal fees), and for property, capital improvements.
- Gain or loss. Proceeds minus cost base, for each parcel sold.
- Losses. Capital losses carried forward from earlier years and losses made this year are taken off this year's gains. The ATO says you can choose which gains they reduce; taking them off gains that do not get the discount first gives the lowest result, and that is what the calculator does.
- Discount. Australian-resident individuals halve what is left of each gain on an asset owned for at least 12 months, counting from the day after acquisition to the day before the CGT event.
- Net capital gain. The total goes in your tax return and is taxed at your marginal rate along with your other income. A net capital loss cannot reduce other income; it carries forward.
Three ways to use it
Quick calculator
For one asset: enter the dates, prices and costs and see the gain, whether the discount applies, the net capital gain and an estimate of the extra tax. The 12-month anniversary is shown so you can see how close a sale was to qualifying.
All your transactions
For a share or crypto portfolio, enter every buy, sell, dividend reinvestment (DRP) and split. The calculator matches each sale to the parcels it came from, works out every financial year in order, and carries losses forward from one year to the next. Change the matching method and watch the result update.
CSV import
Most brokers and exchanges export trade history as CSV. The calculator recognises common layouts (CommSec, SelfWealth, Stake, Pearler, Sharesight, CoinSpot, Swyftx, Binance, Kraken) by their column headings, and for anything else lets you match the columns by hand. Check the imported rows: export formats change and the mappings have not been tested against every current file.
The financial-year view
For each year with a sale you see the figures the tax return asks for at question 18: total current year capital gains (label H), the net capital gain (label A) and net capital losses carried forward (label V), together with the losses applied, the discount, and every disposal with the parcels it came from, how long each was held and whether the discount applied. Enter your other taxable income for an estimate of the extra tax, using the ATO's resident rates for that year and the 2% Medicare levy. The estimate leaves out offsets such as the low income tax offset and the Medicare levy surcharge, so treat it as a guide.
What it does not do
- Indexation for assets bought before 21 September 1999 (most people do better with the discount).
- Partial main residence exemptions, the six-year absence rule, and small business concessions.
- Apportioning the discount for part-year foreign residents.
- Looking up prices: you enter the AUD values, including the market value of crypto received in a swap.
- Return of capital, demergers, rights issues and other corporate actions, beyond splits and consolidations.
Where your situation involves any of these, the schedule's notes page says so, so your accountant can pick it up.
The schedule for your accountant
The free calculator shows everything on screen. The paid CGT schedule (A$14.99 per financial year) produces a PDF with every disposal and matched parcel, the question 18 totals and a notes page listing the method and assumptions, plus a CSV your accountant can import. It is a convenience, not a requirement: you can copy the totals from the screen.
Privacy
Your trades never leave this browser. The calculator runs entirely in the page, stores your transactions in the browser's own database, and works offline after the first visit. Export a backup to move to another device.
Checking the result before you lodge
A calculator is only as good as the figures you give it. Before copying anything into your tax return, run through these checks:
- Holdings reconcile. The units left over after every sale should match what your broker, share registry or exchange says you still hold. If they do not, a buy, DRP or split is missing, and the cost base of some sale is wrong.
- Dates are trade or contract dates. Settlement dates move sales across 30 June and across the 12-month mark.
- Costs are on the right side. Purchase costs belong to the buy; selling costs belong to the sale. Entering both on one side gives the same gain but the wrong cost base for the parcels that are left.
- Losses brought forward match last year's return. The figure at label V of last year's return is this year's starting point.
- Pre-filled data. The ATO pre-fills some share and crypto data from brokers and exchanges. It often lacks cost bases, so treat it as a list of sales to account for, not as the answer.
If a disposal looks wrong, open its parcel breakdown in the year view: each line shows the parcel, its acquisition date, days held and cost base, which is usually enough to spot the missing or mistyped transaction.
Where the rules come from
The discount, the 12-month counting rule, the treatment of losses and the tax rates are taken from the ATO's published guidance, listed under sources below with the date they were last checked. Rates are stored per financial year and updated each July. Where a rule could not be confirmed against an official page, it is marked as unverified in the calculator's notes and in the schedule, so you and your accountant know what to check.