In such a situation, it is best to use e-mail confirmations of execution of deposit or withdrawal instructions to/from the exchange. If this is also not possible, please describe in as much detail as possible the flow of funds that are being verified so that it is possible to verify information about them in external sources of information related to the blockchain.
Alternatively, please provide your annual tax return for the period in which your cryptocurrency purchases were made to document / substantiate your ability to purchase them.
