If a SEPA direct debit transaction fails or if a consumer cancels the transaction, the consumer's bank may charge Mollie extra costs for this. Mollie will charge these costs of € 4,50 to you. This will not be the case for every failed transaction or cancellation, but depends on the bank of the consumer. Dutch and Belgian banks do not do this. The extra costs are charged on top of the normal rates of failed transactions (€ 0,25) and chargebacks (€ 7,50).
Because it depends on the bank of the consumer, it is not entirely clear in advance when these costs will be charged. This means that you will only see the extra costs when you receive the invoice.