Reconstructing Missing Crypto History

Your crypto tax tool flags that the history is missing for one or more assets. This may sound harmless, but it has massive implications for tax calculations: without a complete transaction history, the tool sets the cost basis to zero euros. The result is fictitious gains that never actually occurred. This article shows you step by step how to reconstruct missing crypto history and restore your crypto accounting to a solid foundation, whether you work with Blockpit, CoinTracking, or Koinly.

01 The Problem: Missing History and Cost Basis 0

When your tax tool flags that the history is missing for an asset, it means: there is a receipt for this asset (e.g., a deposit to an exchange or wallet), but the previous transaction documenting the acquisition is missing. The tool cannot trace where the asset came from, what it originally cost, or when it was acquired.

The consequence is severe: in this case, the tool sets the cost basis to zero euros. When sold later, the entire proceeds are calculated as profit, even though you purchased the asset at a specific price.

The more assets affected, the more distorted the entire tax report becomes. For portfolios with many transfers between exchanges and wallets, the sum of fictitious gains can quickly reach five figures.

02 Why Is the History Missing?

The causes of missing history can be divided into five typical categories. They are the same across tools: a tool can only calculate with the data that comes in, and what is missing it cannot know. Often, several occur simultaneously.

• Missing Exchange Imports – Old accounts on exchanges that are no longer actively used were never imported into the tool. This often affects the first exchange where someone bought crypto.
• Missing Data Sources – Exchanges and wallets that were never imported into the tool. Older exchange accounts or wallets on chains that the user forgot are particularly often missing.
• Incomplete Wallet Tracking – Anyone who moves assets across multiple chains (Ethereum, Solana, Polygon, Arbitrum) must record each chain separately in the tool. If a chain is missing, so are the associated transactions.
• Manual Entries & Auto-Balancing – Users try to close gaps with manual entries or Blockpit's "auto-balancing" function. Both create transactions with a cost basis of €0, which visually solve the problem but worsen it for tax purposes.
• Bridges and Wrapped Tokens – Cross-chain bridges technically create a new transaction on the destination chain. If the tool doesn't correctly recognize the bridge transfer as a link, it appears as if the asset appeared out of nowhere on the destination chain.

Source: Help centers of Blockpit, CoinTracking and Koinly

03 How to Identify Missing History in Any Tool

Missing history manifests at multiple levels, similar in every tool. The earlier you recognize the signs, the more precisely you can correct them.

• Direct notice on the asset – The tool marks affected positions: "Missing History" in Blockpit, "Missing Transactions" and tax-report warnings in CoinTracking, "Missing acquisition price" in Koinly. This is the most obvious indicator.
• Unrealistically High Gains in Tax Report – If the calculated gain is significantly higher than expected, a missing cost basis is often the cause. Check the largest gain positions individually.
• Negative or Missing Cost Basis – Some assets show a cost basis of €0 or negative holdings. Both indicate missing incoming transactions.
• Assets Appear "Out of Nowhere" – If an asset suddenly appears in the portfolio without a documented purchase transaction, the origin is missing. This often affects transfers from external wallets or exchanges.

A practical trick: most tools have a filter for exactly these notices. In Blockpit the path runs via Transactions → Filter → Notice → Missing History, in CoinTracking via Analysis → Checks → Missing Transactions, in Koinly via Transactions → Warnings. Going through these filters before every report catches a large share of the errors.

04 Step by Step: Reconstructing History

Reconstructing missing crypto history follows a clear sequence. The more systematically you proceed, the fewer gaps remain.

Step 1: List All Sources

Create a complete list of all exchanges, wallets, and DeFi protocols you've ever used. Also consider platforms you only used briefly or years ago. Typical forgotten sources:

• First Exchange – Where did you buy crypto for the very first time? Bitcoin.de, Bitpanda, Coinbase?
• Intermediate Exchanges – Did you transfer assets to another exchange to buy specific altcoins? Binance, KuCoin, Gate.io?
• Hardware Wallets – Ledger, Trezor, or other cold wallets where you stored assets long-term.
• DeFi Protocols – Uniswap, Aave, Curve, Lido, Jupiter, and other protocols you've interacted with.
• Multi-Chain Wallets – MetaMask, Phantom, Rabby with activity on various chains.

Step 2: Obtain CSV Exports

For each identified source, you need the transaction data. For active exchanges, you can download CSV exports directly. For inactive exchanges or exchanges where you no longer have access, there are alternatives:

• Active Exchanges – Log in and export the complete transaction history as CSV. Make sure to select the entire period, not just the current year.
• Inactive Accounts – Many exchanges allow exports even for inactive accounts as long as the account still exists. Reset the password if necessary.
• GDPR Data Request – If the normal export doesn't work, you can submit a data request under Art. 15 GDPR. The exchange is obligated to provide your stored data.

Whether Binance, Kraken, MEXC or a closed exchange like FTX: how easy or difficult it is to retrieve historical data varies significantly by platform. Exchange history overview: what data you can get and how shows the most common exchanges and their specifics.

Step 3: Check On-Chain Data

For DeFi transactions and wallet activities, blockchain explorers are the central source of information. Every transaction is permanently stored on-chain and can be traced:

• Etherscan – For Ethereum and ERC-20 tokens
• Solscan – For Solana and SPL tokens
• Arbiscan – For Arbitrum
• Polygonscan – For Polygon
• BscScan – For BNB Chain

Enter your wallet address in the respective explorer and check the transaction history. Compare this with the transactions recorded in your tool. Every transaction visible in the explorer but missing in your tool must be added.

Step 4: Import and Trigger Recalculation

Import the obtained CSV files into your tool. Pay attention to the correct format – most tools offer their own import template for each exchange. After importing, it's important to trigger the recalculation. In Blockpit, for instance, the tax calculation doesn't update automatically after each import; the recalculation runs manually via a button in the tax report section. CoinTracking, by contrast, often re-classifies correctly by itself once the real source is added, which is why adding the source beats manual entries here.

Step 5: Check Manual Entries and Auto-Balancing

Check all manual entries and automatically generated balancing transactions. Entries with a cost basis of €0 should be replaced with properly documented transactions – based on on-chain data or CSV exports. Blockpit's auto-balancing and a manual balancing entry visually resolve the notice, but the cost basis remains at €0, which distorts the tax calculation.

If you work specifically with Blockpit and just want to clear the "Missing History" notices there quickly, you'll find the compact tool fix step by step at Fix Missing History in Blockpit. This article here delivers the comprehensive reconstruction across all sources and tools.

Source: Help centers of Blockpit, CoinTracking and Koinly

05 How Reliable Is Each Data Source?

Not every reconstructed transaction is equally well documented. When you close a gap, what matters is not just that a value sits in the tool, but how verifiable it is. That becomes important the moment someone else questions the documentation: the tax office after a DAC8 reconciliation, a tax advisor during a plausibility check, or a bank requesting a proof of funds. From over 500 cases, the reliability of sources falls into three clear tiers.

In practice this means: when reconstructing, work from the top down. First everything that is verifiable on-chain, then the exchange exports, and only what is still missing through a justified manual entry. TX-Partner deliberately builds every reconstruction on the highest possible evidence tier and only falls back on a manual entry when no stronger source exists. Documentation that is largely on-chain-backed holds up to scrutiny. Documentation made of nothing but unproven estimates collapses at the first close look.

06 Special Cases: DEX, Bridges and Missing Exchange Exports

Some situations require more effort than a simple CSV import. Here are the most common special cases and how to handle them.

Closed Exchanges (FTX, Mt.Gox, etc.)

For exchanges that no longer exist or were closed due to insolvency, regular data export is no longer possible. There are still ways:

• GDPR Data Request to Insolvency Administrator – In many cases, user data is stored with an insolvency administrator. A formal GDPR request can provide access to your own transaction data.
• Personal Records – Email confirmations, screenshots, or old CSV exports you saved locally can serve as proof.
• On-Chain Data – Deposits and withdrawals to and from the exchange are traceable on-chain, even if the exchange no longer exists. However, trades within the exchange are off-chain and therefore not reconstructible via blockchain explorer.

Which source helps most depends on the platform. The following overview summarizes the best-known closed or insolvent exchanges and the most realistic route to the data for each. TX-Partner reconstructs the history of closed exchanges via the on-chain trail of deposits and withdrawals, even when the platform itself no longer provides an export.

Receiving a Payout from Insolvency? (Mt. Gox, FTX, Celsius)

One point that affects many people in 2026 and regularly lands wrong in the tool: payouts from insolvency proceedings. Anyone who gets coins or money back from the Mt. Gox or FTX process initially sees only a new receipt in the tax tool, appearing out of nowhere. The tool only knows the incoming amount, not the backstory. If you do nothing about it, it treats the payout like a free inflow with a cost basis of 0.

That is precisely wrong. The payout is the continuation of your original acquisition. What needs to be reconstructed is not today's receipt, but the purchase from back then: when and at what rate did you buy the coins at the time and deposit them onto the exchange? This original cost basis and the original acquisition date have to be documented separately and assigned to the payout, otherwise the tool calculates the full proceeds as profit on the later sale. The building blocks are the same as above: the on-chain deposit from back then, old exports, bank statements of the original fiat payment. How this payout is to be classified for tax purposes (such as the question of holding periods) belongs on your tax advisor's desk; your job in the documentation is to record the original acquisition cleanly and with evidence.

Very Old Transactions (2015-2018)

Transactions from the early years of crypto adoption are particularly difficult to reconstruct. Exchange interfaces and export formats have changed multiple times since then, and some platforms no longer exist. However:

• Blockchain Explorer – On-chain transactions are immutable and fully viewable even after years. Historical prices can be determined via CoinGecko or CoinMarketCap.
• Historical Prices – For manual import into your tool, you need the rate at the time of the transaction. Historical price data is freely available on multiple platforms.
• Manual Entries – Most tools allow manual transaction entries. For individual, clearly traceable transactions, this is the pragmatic solution.

DeFi Protocols Without Tool Integration

Not every DeFi protocol is directly supported by every tool. For protocols without integration, there are two approaches:

• Manual CSV Import – Create a CSV file in your tool's standard format and enter the transactions manually. The necessary data (timestamp, token, amount, rate) can be found via the blockchain explorer.
• Wallet Tracking – If you've entered the wallet address in your tool, most tools automatically recognize many DeFi transactions. However, check whether all transactions were correctly classified – especially for complex interactions like flash loans or composable strategies.

07 The Logic Chain: Why Crypto Accounting Is Critical

Missing history is not an isolated problem. It stands at the beginning of a chain that runs through the entire tax calculation.

If the transaction history has gaps, the tool calculates with a cost basis of €0. Any tax calculation based on this is incorrect. And since DAC8, the tax authority can compare the reported exchange data with the tax return. Incomplete crypto accounting can then lead to inquiries.

Source: Official Journal of the EU, Directive (EU) 2023/2226

08 What Missing History Means for Your Tax Report

Missing history is not just a technical problem in your tax tool. It directly distorts the tax report your crypto tax tool calculates. The larger the portfolio and the tighter the regulations, the bigger this effect becomes.

Since DAC8, tax authorities can systematically compare reported exchange data with the submitted values. If you discover missing history in the tax report, the first step is to correct the data basis so the report reflects the real values. How an already submitted return needs to be adjusted is a question for professional tax advice; the cleaner the documentation, the simpler this step.

09 When Professional Help Makes Sense

Reconstructing missing crypto history is doable yourself in simple cases: import a forgotten exchange, upload a few CSV files, trigger recalculation. However, with more complex portfolios, the effort quickly becomes exponential.

Professional support for crypto accounting makes sense when one or more of the following criteria apply:

• Many Sources – More than 10 exchanges, wallets, or DeFi protocols over several years.
• Complex DeFi Usage – Liquidity pools, yield farming, bridges, wrapped tokens, staking across multiple chains.
• Multi-Year Gaps – Transactions from 2017 or 2018 that were never documented and must now be caught up.
• Closed Exchanges – Platforms like FTX where regular data export is no longer possible.
• Manual Entries with Zero Cost Basis – Transactions were created manually or via auto-balancing with a cost basis of €0 and must be properly documented.
• Errors in Tax Report – The calculated gain significantly deviates from reality and the cause is not immediately apparent.

TX-Partner specializes in exactly these cases: preparing the transaction history in the crypto tax tool completely and comprehensibly. TX-Partner does not offer tax advice, but rather the crypto accounting that tax advisors and tax authorities need as a foundation.

If you're unsure whether your case requires professional support, a non-binding documentation check is the fastest way to gain clarity. In 30 minutes, we assess how extensive the reconstruction is and what effort is realistically involved.