@Braguette
A transaction ID is not a personal information, but a code created pseudo-randomly, so it would be an error to cover it in a Privacy Notice and Terms document. Anyway it is stored in the payment processor database forever. If a customer asks for a refund, she must provide the needed data to make the refund possible, or simply ask the payment processor for a refund via the proper procedure implemented both in 2Checkout and PayPal.
If the payment was delivered directly without intermediaries (i.e. through cryptocurrency which we accept cutting out any intermediary), the customer asking for a refund must again provide us with the proper data to let us verify refund eligibility, for example transaction hash in a blockchain.
Kind regards