Your tax software can only rebuild what you can prove. If you bought 0.5 BTC in 2021, moved it to a hardware wallet, swapped part of it for ETH on a decentralized exchange, and later sold that ETH, the software needs every one of those steps to compute a gain. Skip the swap, and it sees a $22,000 cost basis with no disposal — until you sell the ETH and it has no idea where the asset came from.
That gap is what keeping records for crypto tax filing is really about. Not a shoebox of screenshots, but a habit: export the data when the trade happens, store it where you will find it later, and reconcile on a schedule. Miss one cost basis entry and a tax authority can treat the entire proceeds as gain.
What counts as a record (and what doesn't)
A record ties a specific amount of crypto to a specific date, price, and wallet. A screenshot of your portfolio balance is not a record. It shows you own something. It does not show what you paid.
The four data points every entry needs
At minimum, capture the date and time (UTC is safest), the asset and quantity, the fiat value at the moment of the transaction, and the wallet or exchange it moved through. If you swapped ETH for USDC, you need both sides — the ETH disposed and the USDC received — plus the fee paid in ETH or gas.
Things people forget to log
- Gas fees on failed transactions, which are still a cost and still deductible in many jurisdictions
- Airdrops and fork distributions, which usually count as ordinary income at receipt
- Staking and liquidity provision rewards, taxed when received, not when sold
- Transfers between your own wallets — not taxable, but essential for cost basis tracking
- Small "dust" conversions some exchanges perform automatically
That last one trips up more filers than you would expect. An exchange that auto-converts leftover balances can generate dozens of taxable disposals you never consciously made.
Why exchange exports alone won't save you
An exchange CSV shows the trades you made on that exchange. It shows nothing about the on-chain swap, because that happened on a decentralized protocol. If you sell the resulting ETH for $14,200 and cannot document the original BTC purchase — say the exchange shut down and purged your account history — the gain calculation collapses. You are left arguing with a number you cannot support.
On-chain data is your backup
Block explorers and portfolio trackers can rebuild transaction history from wallet addresses, which is why keeping a list of every address you have used matters as much as the CSV files. Label your wallets. A wallet named "cold storage 2022" is worth more at tax time than one named "0x7a3f..."
Building a system you'll actually maintain
The best record-keeping method is the one that survives a busy month. Pick a cadence and stick to it.
Monthly export, quarterly reconcile
On the first of each month, export CSVs from every exchange and wallet you used. Drop them in a dated folder; cloud storage works fine. Once a quarter, open your portfolio tracker and check that the transaction count matches. Discrepancies usually mean a missing API connection or a wallet you forgot to add.
What to store alongside the numbers
| Record type | Why it matters |
|---|---|
| Exchange CSV exports | Cost basis and proceeds for custodial trades |
| Wallet address list | Reconstructs on-chain activity if a service dies |
| Bank and card statements | Proves fiat on-ramps when exchange data is missing |
| Fee receipts | Supports deduction claims and adjusts basis |
Keep these for as long as your jurisdiction requires. In the US, that is generally three years from filing, but longer if you underreport income significantly. Do not shred anything you are unsure about.
Tools, spreadsheets, and when to hand it off
A spreadsheet works if your volume is low — under a few hundred transactions a year, say. Beyond that, manual entry invites errors, and errors compound. Crypto tax software can import exchange APIs and wallet addresses, but it is only as good as the data you feed it. Garbage in, audit risk out.
If you trade across multiple chains, use DeFi protocols, or hold assets through a bear market and back, a tax professional who understands crypto is cheaper than a penalty. Platforms like MGBX can help you track activity across accounts, but the responsibility for accurate records stays with you. No tool fixes a missing year of history.
Start this week: pick one exchange, export its full transaction history, and count the gaps. That number is your baseline — and the first thing to fix before the next filing deadline.
Frequently asked questions
Do I need to record transfers between my own wallets?
Yes, even though they are not taxable events. Transfers establish the chain of custody for your cost basis. Without them, software cannot tell whether crypto leaving one wallet was a sale or just a move to cold storage. Record the date, amount, and both addresses every time.
How long should I keep crypto tax records?
It depends on where you live. Many jurisdictions require three to seven years after filing, and some keep the window open longer for unreported income. When in doubt, keep everything — digital storage is cheap, and reconstructing old exchange data after an account closes is often impossible.
What if my exchange no longer exists?
This is why you export proactively. If a platform shuts down, your only remaining proof may be bank statements, emails, and on-chain records tied to your wallet addresses. Pull your data before you need it, not after.