Terminology

Use of Must / Should / Can / May

These implementation guides use the following terminology to indicate the importance of functionality or a recommendation:

• Must (not): Mandatory to include/do

• Should (not): Best practice to do/include and highly recommended to do/include to avoid extra work/impact. Only ignore if this clashes with local practices/law

• Can/Could (not): Suggestion which could improve the user experiences, lower (implementation running) costs/effort and/or reduce risk, but these results can be achieved/solved in other ways. Not mandatory to incorporate.

• May (not) / Is (not) allowed to: This is functionality or a choice left up to the IPSO, PSP, SAP or FX Provider

Nexus-specific terminology

This guide refers to a number of actors in Nexus: Payment Service Providers (PSPs), Instant Payment System Operators (IPSOs), Foreign Exchange Providers (FXPs) and Settlement Account Providers (SAPs).

For a primer on each of these actors please see Chapter 2.3 of the Nexus (2024) report.

ISO 20022 Terminology

This guide uses the following ISO 20022 terminology:

• Debtor is the sender of the payment. In this document, the Debtor is referred to as Sender.

• Debtor Agent is the PSP or bank that holds an account for the Debtor. In this document, the Debtor Agent is referred to as the Source PSP.

• Creditor is the intended recipient of the payment. In this document, the Creditor is referred to as Recipient.

• Creditor Agent is the PSP or bank that holds an account for the Recipient. The Creditor Agent is referred to in this document as the Destination PSP.

• Proxy (also known as alias) is a piece of information, such as a mobile phone number, that can be associated with an account.

  • We use the term Proxy Directory to refer to the database of proxies (aliases) and the accounts they are associated to, and Proxy Directory Operator (PDO) to refer to the operator of the Proxy Directory service (who may also be the same entity as the Instant Payment System Operator). No equivalent terminology exists in ISO 20022.

• Element is a data field in an ISO 20022 XML message.

Guideline to ISO 20022 notation

The following notation is used when referring to ISO 20022 elements:

• For readability, the path to an element is written with unabbreviated element names, with the symbol > separating each element. Users should refer to the official usage guidelines for the equivalent abbreviated path.

• The top-level <Document> element is not listed

• The top-level message wrapper (eg FI to FI Customer Credit Transfer) is omitted if the message in question is obvious from the content on the page

• Three dots are used to show that the higher levels of a message structure have been omitted. For example, for pacs.008:

• Credit Transfer Transaction Information > Payment Identification > UETR

• … > Debtor Account > Identification > IBAN

Other terms used

• Corridor – the payment route between two currencies in two different countries

• Currency pair – the source currency and destination currency (in a particular direction). Often written as XXXYYY, for example SGDEUR relates to a payment where the Source Currency is Singapore dollars and the Destination Currency is euro.

• Base Rate – the basic, unimproved rate provided by the FXP to Nexus for a specific currency pair

• Final Rate – the rate provided by Nexus to a PSP once any relevant tier-based or PSP-based improvements have been applied to the base rate. It is the ratio between the amount the Source PSP pays to the FXP and the amount the FXP pays to the Destination PSP.

• Effective Rate – the effective rate paid by the Sender, with potential fees included. See Quotes for further explanation.