According to the 2026 Independent Reserve Cryptocurrency Index, one in three Australians now own crypto. However, some bought their crypto years ago through platforms that have since closed or changed. As a result, finding the original purchase records can be difficult, making it harder to establish the correct cost base. Fortunately, you can often reconstruct these records using other sources.
The Australian Taxation Office (ATO) recommends using exchange records and blockchain explorers to rebuild missing information. By combining this evidence with Australian dollar values from each transaction date, you can reconstruct your cost base. However, if the evidence is insufficient, the ATO does not provide a default figure. This guide explains where to find the necessary records, how to reconstruct your cost base, and how to document your calculations.
Key Takeaways
- A crypto cost base mainly includes the price paid plus incidental costs such as fees.
- The ATO suggests exchange support teams and blockchain explorers to recreate missing records.
- Each rebuilt figure must be valued in Australian dollars on the original transaction date.
- The ATO has no fallback cost base for crypto, so document every reconstruction step.
Why Do Crypto Cost Base Records Go Missing?
Crypto cost base records can be difficult to recover when transaction history is spread across exchanges and wallets. If an exchange closes or an account becomes inaccessible, original purchase details may be lost. Frequent transfers can also make it harder to trace an asset back to its original purchase.
Exchanges That Close Or Lock Accounts
The ATO’s crypto reporting guidance warns that exchanges can close and access can be lost. Once that happens, years of purchase history may be impossible to download. Forgotten logins and closed accounts create the same problem on a smaller scale. The cost base still has to be proven, even if the platform is gone.
Transfers Between Wallets And Platforms
Moving crypto between your own wallets is generally not a taxable disposal if beneficial ownership stays the same. However, transfers can complicate record-keeping when the original purchase was made through another wallet or exchange.
Relying On Exchange Records Alone
Many investors treat their exchange account as their only record. The ATO says that approach is not enough, because investors must keep their own records. Exchange reports also often miss the cost of coins transferred in from elsewhere. Our guide to how the ATO tracks your crypto shows what exchanges already report.
What Makes Up A Crypto Cost Base?
A crypto cost base is generally what you paid plus certain related costs. The ATO’s cost base guidance lists five elements, though only some apply to crypto. Knowing which matter tells you exactly what evidence to find. Our complete guide to crypto tax in Australia covers how the cost base feeds into each gain.
Money Or Property Given For The Crypto
The first element is the money paid for the crypto. Where you gave property instead, such as other crypto, its market value counts. This is usually the largest part of any cost base. It is also the figure most often lost when records disappear. For bank-funded purchases, this is where bank statements become valuable.
Incidental Costs Such As Transfer And Broker Fees
The second element covers incidental costs of acquiring or disposing of the crypto. For crypto, that usually means broker fees, costs of transfer and payments to an accountant or adviser. Tax advice counts only if a recognised tax adviser provided it. Any cost you can claim as a deduction stays out of the cost base.
Converting Foreign Currency Amounts
Crypto bought with US dollars or another currency must be converted to Australian dollars. The ATO requires the exchange rate at the time of the transaction, not today’s rate. The ATO has used Reserve Bank of Australia rates since 1 January 2020. Rebuilt records need that historical rate beside every foreign amount.
The Reduced Cost Base For Capital Losses
If a rebuilt record shows a loss, you work it out using the reduced cost base. It has the same elements, except the third element of ownership costs is replaced. Ownership costs rarely apply to crypto, so both figures are often identical. Our guide to lost and stolen crypto covers loss claims in more depth.
Where Can You Find Evidence To Rebuild Missing Records?
Evidence for a missing cost base is usually scattered across several places. For missing capital gains tax (CGT) records, the ATO points investors back to third parties. For crypto, those third parties are exchanges, banks and the blockchain itself. Start with the most reliable source and work outwards from there.
Exchange Customer Service And Old Exports
The ATO’s crypto record-keeping guidance suggests contacting an exchange’s customer service to recover lost records. Some platforms can supply full histories for closed or dormant accounts on request. Check old downloads, cloud storage and email attachments for earlier exports too. A single forgotten file can restore years of cost base data.
Blockchain Explorers
The same ATO guidance also suggests using a blockchain explorer. Enter a wallet address and the explorer shows every incoming and outgoing transfer, with dates. It confirms when coins arrived and in what quantity. It does not show the price paid, so pair it with historical price data in Australian dollars.
Bank And Card Statements
Bank and card statements show the Australian dollars that left your account to buy crypto. A deposit to an exchange, matched with a purchase date, can support the money paid. Banks can usually supply statements going back several years. Match each deposit to the coins it bought, not just the account it funded.
Emails, Screenshots And Past Tax Returns
Exchanges often email trade confirmations, so search your inbox for platform names and order numbers. Screenshots of balances or trades can also support dates and quantities. Past tax returns and tax software reports may already contain calculated cost bases. Together, these fragments often fill gaps that no single source can.
How To Reconstruct A Missing Crypto Cost Base?
Reconstructing a cost base works best as a structured process rather than a random hunt for receipts. The steps below build each figure from evidence, then record how it was reached. Following them in order keeps every rebuilt amount traceable. That traceability matters most if the ATO later asks questions.
Step 1: List Every Acquisition You Know Of
Start by listing every purchase, swap, reward and transfer that you can remember. Include the platform, approximate date and quantity for each one. Then compare the list with your current holdings. Any coins you hold without a matching acquisition point to a record still missing. This gap list becomes your working checklist.
Step 2: Match Evidence To Each Acquisition
Work through the list and attach evidence to every single entry. A blockchain transfer might confirm the date, while a bank statement confirms the money paid. The strongest entries combine two or more sources that agree. Where sources conflict, note the difference and investigate, rather than picking the convenient figure.
Step 3: Value Each Acquisition In Australian Dollars
Each acquisition needs its value in Australian dollars on the day it happened. Where you paid in Australian dollars, the bank or exchange record gives that figure directly. Otherwise, apply the historical exchange rate noted in the cost base section above. Record the rate source next to every converted amount.
Step 4: Rebuild Crypto-To-Crypto Swaps At Market Value
Swaps need special care, because no Australian dollars change hands. Under the ATO’s crypto transactions guidance, a swap is a disposal of the crypto given up. The new crypto’s cost base is its market value at the time of the swap. Historical price data for that date usually rebuilds it.
Step 5: Add Incidental Costs
Once the main figure is rebuilt, add any incidental costs that relate to it. Exchange fees often appear in trade confirmations or account exports. Network fees for transfers can be checked on a blockchain explorer. Leave out anything already claimed as a deduction. Small fees add up across hundreds of trades.
Step 6: Document How Each Figure Was Rebuilt
Finally, write down how every reconstructed figure was reached and which sources support it. Keep copies of the supporting evidence alongside that note. The ATO’s CGT calculator and record keeping tool can store the rebuilt figures through myGov. A clear trail makes each rebuilt figure far easier to defend later.
How Do You Work Out Which Crypto Units You Sold?
Rebuilt records often show several purchases of the same coin at different prices. When only part of a holding was sold, you need to decide which units went. That choice changes both the cost base and whether the CGT discount applies. The ATO has guidance on this, but only for shares and units.
The ATO's Approach For Shares And Units
For shares and units, the ATO’s guidance on identifying units sold sets out three options:
- Identifying the exact units sold, where records allow
- Accepting your own selection of the units disposed of
- Using a first in, first out basis, treating the earliest units bought as sold first
An average cost method is allowed only in limited cases. One example is identical shares acquired on the same day.
Applying A Consistent Method To Crypto
The ATO has not published equivalent guidance specifically for crypto. Some investors and advisers apply the share approach to crypto by analogy. Whichever method you use, apply it consistently and record it with your reconstruction notes. If you are unsure, a registered tax agent can confirm the approach for your situation.
What If A Cost Base Cannot Be Fully Rebuilt?
Sometimes evidence runs out before every single figure is rebuilt. The ATO expects records for every transaction relevant to a capital gain or loss. It does not, however, publish a crypto-specific rule for figures that cannot be proven. That makes careful handling of any remaining gaps all the more essential.
Why There Is No ATO Fallback Figure For Crypto?
Many online guides say an unproven cost base defaults to zero. That rule largely comes from United States tax practice, not from the ATO. The ATO instead directs you to third parties for copies of missing records. Keep rebuilding until every reasonable source has been exhausted. Only then consider how to treat what remains.
Amending Past Returns Once Records Are Rebuilt
Rebuilt records can show that an earlier return overstated or understated a gain. Individuals generally have two years to amend an assessment, counted from the day after the notice issues. An overstated gain can also be corrected the same way. Our list of common crypto tax filing mistakes shows where these errors usually start.
When To Get Professional Help
Large gaps, many platforms or years of history can make reconstruction complex. A registered tax agent can review your evidence and advise on remaining gaps. If records were lost in a natural disaster, the ATO can also help you reconstruct them. Either route beats guessing and hoping the figures are never questioned.
How Can KoinX Help You Rebuild Missing Cost Base Records?
Rebuilding a cost base by hand means cross-checking exports, statements and blockchain records line by line. KoinX pulls exchange and wallet data into one place and applies ATO rules to it. Gaps then become visible instead of hidden across platforms. The reports and features below target the most common reconstruction problems.
Transaction History Report
The Transaction History Report is a full ledger of trades, transfers, rewards and fees. It becomes the master list for Step 1, showing every acquisition across every connected exchange and wallet. Holdings without a recorded acquisition are then easier to spot. Exported regularly, it also prevents the next gap from forming.
Buy Sell Report
The Buy Sell Report brings every buy, sell and swap into one view. Each purchase shows the price paid, which feeds directly into the first cost base element. Swaps appear alongside purchases, so none are missed during Step 4. Reviewing it before generating final reports helps catch missing trades early.
Internal Transfer Detection
Transfers between your own accounts are where cost base records most often break. Internal Transfer Detection matches a withdrawal on one platform with its deposit on another. The original purchase price then travels with the coins instead of disappearing. A later sale on a different exchange keeps its true cost base.
Quick Edit
Rebuilt records often arrive with gaps, such as a missing price or an unmatched transfer. Quick Edit lets you resolve those errors and warnings the moment they are flagged. That makes it simpler to add reconstructed figures where the evidence supports them. Where the right fix is unclear, the support team can step in.
Every rebuilt figure is only as strong as the evidence behind it. Connect every exchange and wallet you can still access, and let transfers match automatically. Then focus your reconstruction effort on the gaps that remain. Start rebuilding your crypto records with KoinX before your next return is due.
Conclusion
Export exchange histories regularly, and save them somewhere you control. Record wallet addresses and the purpose of each transfer as it happens. Those habits keep cost base evidence intact, even if a platform closes. Five minutes after each trade saves days at tax time.
For records already lost, begin with your largest holdings. Those carry the biggest tax difference if unproven. Smaller gaps can follow once the major figures are secure. A rebuilt cost base also protects any capital loss you plan to claim. Rebuild your cost base on KoinX and keep every figure backed by evidence.
Frequently Asked Questions
Do I Need To Rebuild Records For Crypto I Still Hold?
Yes, because the cost base matters whenever you eventually dispose of the crypto. Evidence is also easier to find now than years from now. Exchanges close, bank statements get harder to obtain and memories fade. Rebuilding while you still hold the crypto turns a future scramble into a routine calculation.
How Long Should I Keep Rebuilt Records?
Keep them for 5 years after the income year in which the CGT event happens. For crypto you still hold, that clock has not started yet. If the records support a net capital loss, keep them until the loss is used. Individuals then keep them for a further two years.
Is A Crypto Gift Rebuilt Differently?
Yes. Crypto received as a gift has no purchase price to find. For gifted assets, the ATO suggests asking a professional valuer what the market value would have been. For crypto, historical price data on the date received usually serves the same purpose. Record the date, quantity and sender alongside that value.
Does Rebuilding Records Change My CGT Discount?
It can, because the discount depends on holding the crypto for at least 12 months. A rebuilt acquisition date may show a coin was held longer than you assumed. That can halve the taxable part of a gain. Without a provable date, claiming the discount becomes much harder to support.
