(23)Furthermore, taking into account that this Regulation undertakes harmonisation for the first time of interchange fees in a context where existing debit card schemes and interchange fees are very different, it is necessary to provide for flexibility for domestic payment cards markets. Therefore, during a reasonable transition period, in relation to domestic debit card transactions, Member States should be able to apply to all domestic debit card transactions within each payment card scheme a weighted average interchange fee of no more than the 0,2 % of the annual average transaction value of all domestic debit card transactions within each payment card scheme. In relation to the interchange fee cap calculated on the annual average transaction value within one payment card scheme, it is sufficient that a payment service provider participates in a payment card scheme (or some other type of agreements among payment service providers) in which, for all domestic debit card transactions, a weighted average interchange fee of no more than the 0,2 % is applied. Here, too, a flat fee or a percentage fee or a combination of the two can be applied provided that the weighted average maximum cap is respected.