Missing transfer data is the most common cause of missing cost basis (MCB)/unknown gains. Unless you have your accounting method set to FIFO, it’s critical that we have a transfer out AND a matching transfer in for each time you move crypto between two platforms. Those matching transfer pairs allow us to track cost basis between platforms, so missing either a transfer in, or a transfer out (or both) will result in MCB when that transferred crypto is disposed.
In this example, I bought one million $SHIB on Huobi, transferred it out from Huobi and into Atomic Wallet, and then traded my $SHIB to $HOGE on Uniswap using my Atomic wallet. I used a CSV to bring in my Huobi trades and connected my Atomic wallet using our ETH wallet integration.
However, I didn’t notice that the export I got from Huobi only listed my trades and not my transfers (often referred to as deposits and withdrawals). Since we don’t have that transfer out transaction from Huobi, we are getting an "Unknown Gains" flag, which indicates that we are missing cost basis for that disposal.
It’s very common for transfer data to be missing from an exchange, but it’s an easy fix! In order to resolve the "Unknown Gains" flag, all we need to do is upload my Huobi transfer data so that my transfer out of 1000000 $SHIB will appear.
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