The aim of the following article is to present the issues of the planned legal regulation of a new, specific category of the participant of payment services market - third-party payment service provider. This is a “third” entity in relation to the user of basic payment service (namely, payer and receiver) as well as to the provider of the payment services - an account-holding institution. Introduction of this term into European Union legislation is one of the most significant changes in the project of a new Payment Services Directive (PSD II). Particularly important in this context is the need for exact definition of legal status of the third-party payment service providers as well as precise determination of the boundaries of their respons...