In order to get access to a payment system, a settlement account with a central bank is required. Today in most jurisdictions, non-bank PSPs can't directly access payment systems, as they are not allowed to obtain settlement accounts. Legal barriers in PSD2 and the Settlement Finality Directive (SFD) force non-bank PSPs to open accounts at commercial banks - often competing with non-banks to some extent - to indirectly access payment systems. 

In general, there are two types of access to payment systems available to PSPs:

1. Direct access, where a direct participant in a payment system is a party that instructs, clears and settles payments on its own behalf; direct participation requires the participant to have a central bank account of some kind (e.g. a settlement account).
2. Indirect access, where a PSP can access a payment system via a direct participant acting as its intermediary. The direct participant clears and/or settles funds on behalf of the indirect participant.