(16)As a consequence of unilateral undertakings and commitments accepted in the framework of competition proceedings, many cross-border card-based payment transactions in the Union are already carried out respecting the maximum interchange fees. In order to provide for fair competition in the market for acquiring services, the provisions relating to cross-border and to domestic transactions should apply simultaneously and within a reasonable period after the entry into force of this Regulation, taking account of the difficulty and complexity of the migration of payment card schemes, which this Regulation necessitates.