Crypto cost basis methods in Australia: how the ATO expects you to calculate gains

When you sell cryptocurrency in Australia, the capital gain or loss you report depends entirely on which cost you assign to the coins you sold. That calculation is determined by your cost basis method. The ATO doesn't prescribe one fixed method, but it does require you to pick one and apply it consistently across all your disposals for a given asset. Getting this wrong doesn't just affect your tax bill for one year. It can compound errors across every subsequent disposal.

What cost basis actually means

Cost basis is the original purchase price of an asset, including any fees paid at acquisition. When you dispose of a crypto asset, whether by selling it, trading it for another token, or using it to pay for something, your capital gain equals the proceeds minus the cost basis of the coins you disposed of.

The complication for crypto investors is that most people accumulate the same asset across multiple purchases at different prices. If you bought Bitcoin in four separate transactions over two years, each parcel has a different cost. When you sell a portion of your holdings, the ATO needs to know which parcels you're treating as sold. That's where the cost basis method comes in.

The three main methods recognised in practice

The ATO hasn't published a binding list of approved methods for crypto, but its general CGT guidance, combined with rulings on other asset classes, points to three approaches that Australian investors use:

• First In, First Out (FIFO): You treat the earliest-acquired coins as the first ones sold. This is the most common method and the one the ATO's guidance implicitly supports for crypto.
• Last In, First Out (LIFO): You treat the most recently acquired coins as the first ones sold. This method is used in some overseas jurisdictions but its acceptability in Australia is not formally confirmed by the ATO.
• Weighted average cost: You pool all acquisition costs for an asset and divide by the total quantity held, then use that average as the cost basis for each unit sold.

A fourth approach sometimes discussed is Highest In, First Out (HIFO), where you assign the highest purchase price to the coins being disposed of to minimise gains. The ATO has not endorsed HIFO, and using it without clear records to support specific parcel identification is risky.

FIFO and why it's the safest starting point

FIFO is the most defensible method for Australian crypto investors because it aligns with how the ATO applies parcel-based CGT rules across other asset classes, including shares. Under FIFO, your records need to show each acquisition date and price, in order. When you sell, you work from the oldest parcel forward.

FIFO also interacts directly with the 12-month CGT discount. If you hold coins for more than 12 months before selling, you're entitled to a 50% discount on the resulting capital gain. Under FIFO, coins acquired earliest are sold first, which means longer-held parcels get disposed of sooner. That can work in your favour if prices have risen significantly since your earliest purchases. The 12-month CGT discount rules for crypto are worth reviewing before choosing a method, because the interaction between holding period and cost basis method is where most of the tax planning sits.

Weighted average and when it makes sense

Weighted average is simpler to manage for investors who trade frequently. Rather than tracking individual parcels, you recalculate the average cost of your holdings each time you acquire more. When you sell, every unit has the same cost regardless of when it was purchased.

The drawback is that weighted average erases the distinction between short-held and long-held parcels. If you've held some coins for well over 12 months and others for weeks, the weighted average method collapses that distinction. You can't claim the CGT discount on a portion of a disposal under weighted average, because you can't identify specific parcels. For investors with large older holdings, this can be a significant cost.

The consistency requirement

Whichever method you choose, the ATO expects you to use it consistently for the same asset. Switching methods year-to-year to minimise tax in each period is not permitted. If you change your method, you need to be able to justify the change, and the ATO may treat the switch as an attempt to manipulate outcomes.

Consistency also applies across exchanges and wallets. If you hold Bitcoin on three different platforms and you've chosen FIFO, you apply FIFO across all of them, not separately to each account. This requires consolidated records, which is where most investors fall short. Tax software tools that import transaction data from exchanges can automate the parcel tracking, but they often default to their own method without asking. Check which method your software uses before treating its output as final.

Records the ATO expects you to keep

The ATO requires records for every crypto transaction, retained for five years from the date you lodge the relevant return. For cost basis purposes, you need to record the date of each acquisition, the quantity acquired, the price paid in Australian dollars at the time of purchase, and any fees included in the cost base. Exchange confirmations, bank statements showing the AUD transfer, and screenshots of transaction histories all count as supporting records.

Poor records are the most common reason investors can't defend their cost basis calculations. If you can't demonstrate which parcels were sold, the ATO can impose a default calculation, which is rarely in your favour. Investors who've also received tokens through staking, airdrops, or hard forks face additional complexity, because those tokens have a cost basis of either zero or market value at receipt, depending on how they were treated on arrival. The ATO's treatment of hard fork tokens is handled separately to purchased parcels and needs to be tracked as its own acquisition.

Specific parcel identification as an alternative

Some tax advisers recommend specific parcel identification, where you explicitly nominate which parcels you're selling at the time of disposal. This gives you the most flexibility to minimise CGT in any given year, for example by selling your highest-cost parcels first to reduce the gain. The ATO permits this approach for shares, and by extension it applies to crypto. The requirement is that you identify the parcel at the time of the disposal, not retrospectively. That means your records need to be granular enough to support it.

Specific parcel identification is the most powerful method from a tax-minimisation standpoint, but it demands the most rigorous record-keeping. It's most practical for investors who make relatively infrequent large trades rather than daily micro-transactions across multiple platforms.

Choosing a method before you need one

The right time to decide on a cost basis method is before you start accumulating parcels at different prices, not in the week before lodgement. Once you have a diverse acquisition history across multiple exchanges and time periods, reconstructing which method produces the best outcome is complex and may not be possible without professional help.

If you've already accumulated holdings without tracking parcels carefully, start by consolidating your transaction history from all exchanges and wallets into a single ledger. From that ledger, you can then apply whichever method is both permitted and most advantageous given your specific history. Engaging a tax accountant with direct experience in crypto is worth the cost if your holdings span multiple years and exchanges.