I have a client with a 2024 Gain/Loss report from Coinbase showing a Bitcoin sale on 03/05/2024, with an acquisition date of 11/30/2022. However, Coinbase indicates that there's no cost basis on record for this transaction.

Do they need to go back to Coinbase to retrieve this, or is there another way to handle this?

Note: The client made multiple Bitcoin purchases in 2022 at different prices and believes they can download reports of those transactions. If so, can we use those records to calculate the cost basis? Since they didn’t sell all the Bitcoin they bought in 2022, how do we determine which purchase price to use?