13.1.01 What is a payment initiation service (PIS)?

PIS (payment initiation service) is a payment method when the payer in order to pay for goods or services online authorises the payment service provider to access their bank account via the online banking where the service provider creates and executes a transfer.

Or simply explained, with PIS, you give a payment service (Paysera) permission to go into your online banking and pay for your online purchase.