It might seem difficult to classify all transactions without any idea about the source of funds or the receiving address. However, it is crucial for an accurate tax report to classify all transactions in order to be as precise as possible for the tax evaluation of your actions during the tax year. You should take the time to remember or investigate unknown transactions with the help of the data from the blockchain or other records (e.g. personal notes, e-mails, twitter, telegram, discord, etc.) Make sure to update the information in your portfolio frequently and add a comment if you are unsure about the correct classification.