(20)It is important to provide legal certainty to the payments industry on business models for direct debits. Regulation of multilateral interchange fees (MIFs) for direct debits is essential to create neutral conditions of competition between PSPs and so to permit the development of a single market for direct debits. Such fees for transactions which are rejected, refused, returned or reversed because they cannot be properly executed or result in exception processing (so-called ‘R-transactions’ where the letter ‘R’ can signify ‘reject’, ‘refusal’, ‘return’, ‘reversal’, ‘revocation’ or ‘request for cancellation’), could help to allocate costs efficiently within the internal market. Therefore, it would appear beneficial for the creation of an effective European direct debit market to prohibit per transaction MIF. Nevertheless, R-transaction fees should be allowed, provided that they comply with certain conditions. PSPs must provide clear and understandable information to consumers on R-transaction fees in the interests of transparency and consumer protection. In any event, the R-transaction rules are without prejudice to the application of Articles 101 and 102 of the Treaty on the Functioning of the European Union (TFEU). Furthermore, it should be noted that in general direct debits and card payments have different characteristics, in particular in terms of the higher potential for payees to provide incentives for the use of a direct debit by payers through a pre-existing contract between the payee and the payer, whilst for card payments no such prior contract exists and the payment transaction is often an isolated and irregular event. Therefore, the provisions on MIFs for direct debits are without prejudice to the analysis under Union competition rules of MIFs for payment card transactions. Additional optional services are not covered by the prohibition under this Regulation where they are clearly and unequivocally distinct from the core direct debit services and where PSPs and PSUs are completely at liberty to offer or use such services. Nevertheless they remain subject to Union and national competition rules.