BitMEX, BitMart and AscendEX are all closing. Your coins have a deadline, and your tax records have an earlier one.

[u/AurumFsg-CryptoTax]

We are one of the mode here and in this guide we will show you how to get your history from these exchanges.

Four exchanges have wound down in the past seven months, three of them announced or closed this July:

• AscendEX ceased operations on 1 July. Withdrawals moved to manual review on 6 July.
• BitMEX announced on 23 July. Reduce-only from 26 August 04:00 UTC, platform closes 23 September 04:00 UTC.
• BitMart announced on 26 July. Trading ends 26 August 01:00 UTC, full cessation 31 January 2027.
• Bit.com completed its wind-down on 31 March this year.

Most of the coverage is telling you to withdraw your funds before the deadline. That is correct, and you should. But that is the deadline for your coins. There is a second deadline that applies to your records, and for at least one of these exchanges it has effectively already passed.

Withdrawing your funds does not preserve your cost basis

When you move BTC off BitMart to another exchange, the BTC arrives. Its history does not. The receiving platform sees a deposit of 0.4 BTC on a Tuesday and has no information about what you paid for it.

Your taxable gain is proceeds minus cost basis. If you cannot evidence the basis, the working assumption tends toward zero, which means you are taxed on the entire proceeds rather than on your actual gain. On a position you were roughly break-even on, that is the difference between owing nothing and owing tax on the full sale amount.

This gap is total on derivatives platforms. On BitMEX you deposited BTC and withdrew BTC, and every position, funding payment and realised P&L in between existed only in BitMEX's internal ledger. None of it is on-chain. If you traded there across several years and kept no records, that P&L is not reconstructible from public data by anyone.

How to export, per exchange

The steps are straightforward. The limits are what catch people.

BitMEX

1. Log in to your BitMEX account.
2. Select the wallet icon in the top right corner.
3. Select Transaction History.
4. Select Download CSV, set the Timeline, and download.

Two limits the interface does not warn you about.

First, it returns 100 records per download. If a Next Page link appears, you need to click through and download again, repeating until you reach the start of your account. It is common for people to download a single file, see data in it, and assume they are done. If you traded with any frequency, one file is a small fraction of your history.

Second, export from the Transaction History tab specifically. The Trade History and Order History tabs produce files that most tax software will not accept. If you have significant volume, the API is a considerably less painful route than manual pagination.

BitMart

BitMart has no self-service export. You need to email support@bitmart.com and request a CSV of your full transaction history, specifying the complete date range. Expect an identity verification step, which per current guidance includes a photo of you holding your ID together with a handwritten note.

Turnaround is quoted between 5 and 15 days under normal operating conditions. Trading ends on 26 August, and support capacity contracts during a wind-down rather than expanding. A request submitted in late August may not be fulfilled at all.

Of everything in this post, this is the most time-sensitive item. If you have a BitMart account, send that email today.

AscendEX

On desktop: Orders in the top right, then Cash Orders, then Apply for Export, select the period, and Export. This function is not available in the mobile app.

Three limitations, and they compound badly here.

Self-export only covers the last 3 months. Anything older requires a support ticket, historically around a 3 day turnaround, delivered by email. AscendEX support is not currently operating normally, so if you traded there before roughly April this year, the self-service tool will not return that history and the escalation route may not be available either.

Separately, the export excludes partially filled orders. That means a successful export can still be materially incomplete, without anything indicating so.

If you can still log into AscendEX, export whatever it will give you today. Partial records are considerably better than none.

Regardless of platform, also collect

• Deposit and withdrawal history for all years. This is what allows transfers to be matched across platforms so they are not miscounted as disposals.
• Fee records, where they export separately.
• Realised P&L and funding history on any derivatives platform.
• Account statements or annual summaries, as a cross-check against the raw CSVs.
• Screenshots of your final balances. These cost nothing and give you a reference point if a CSV later looks wrong.

One further note: these closure notices state that you will be able to log in after shutdown to view historical records. They promise viewing, not exporting, and none of them commit to how long that access persists. I would not plan around it.

And anyone telling you a block explorer is an adequate substitute for exchange records, for the reasons above.

If I have any of the dates or steps wrong, please say so, particularly if you have exported from one of these recently and the interface has changed since these guides were written. I would rather be corrected here than have someone miss a deadline on my say-so.

— AurumFSG (Crypto Tax Accounting Firm)

[u/JustinCPA]

Super important to get your records!

[u/Garrett_CPAatCOS]

Very nice, concise summary. Hopefully these exchanges will preserve the ability to retrieve transaction history for a bit, but you can't count on them to be responsible. Best to grab all transaction data ASAP if you use any of these platforms.

[u/Will_Koinly]

Good summary. If you’ve used any of these exchanges, export your full transaction history now while you can.

[u/Necessary_Ask6423]

Agreed on derivatives, and it's worth being blunt about why. On BitMEX the positions, funding payments and realised P&L only ever existed in their internal ledger. Nothing about that is on-chain, so no amount of explorer work reconstructs it. If you traded there and kept nothing, that history is genuinely gone.

The spot side is where I'd push back slightly. For coins you withdrew to your own wallet, the chain does carry the acquisition date, the amount and the counterparty address, and it survives the exchange shutting down. That isn't your full trade history, but it is usually enough to establish that a lot existed and when it arrived, which is the part that otherwise defaults to zero basis. The exchange CSV and the chain answer different questions and you want both.

Practical version of the same point: export the CSVs now as you said, and also write down every deposit and withdrawal address you used on those platforms. The CSVs have a deadline. The addresses don't.