Specific Message Elements

Financial institution identification

Any financial institution in Nexus, including PSPs, SAPs (and FXPs), can be identified using either BIC, LEI, or an alternative domestic format (“Clearing System Member Id” in the ISO 20022 standard).

• In case the BIC is used to identify financial institutions (Agents in the ISO 20022 standards), this may be either BIC-11 or BIC-8.

• The Legal Entity Identifier (LEI) is a 20-character, alpha-numeric code based on the ISO 17442 standard developed by the International Organization for Standardization (ISO).

  • The Source PSP should provide its own LEI in the <LEI> element. (This can help to streamline sanctions screening.)

  • Where LEIs for other agents are available, they can also be used (but are not mandatory).

• Clearing System Member Ids need to follow the domestic formatting rules.

• The format of domestic Clearing System Member IDs should be defined by the IPSO (when onboarding with Nexus, using the Nexus Service Desk), as a regular expression, so that it can be shared with Source PSPs when initiating payments to the Destination Country. See Financial Institution Identification.

Retrieving reachable PSPs: Nexus provides the IPSO with the GET PSPs API, allowing for the retrieval of all reachable and non-reachable parties in a specific country. This API will also return additional information on the reachable parties, such as the supported services (for example the support for time critical and non-time critical Nexus payments).

Message and instruction identification

Nexus prescribes two specific reference elements for track & trace purposes across the Nexus network:

Message ID

The message ID in the ISO 20022 XML messages serves as a point-to-point reference and will be assigned by the sending party in each message leg. The message ID should be generated according to the Nexus Usage Guidelines. This message ID must be unique per sending party for at least 2 months and is assigned in the Group Header > Message Identification element.

Unique End-to-end Transaction Reference (UETR)

The UETR is the unique end-to-end transaction reference element, generated according to the Universally Unique Identifier (UUID) algorithm defined in IETF standard RFC 4122, using version 4 of the generation algorithm. The algorithm ensures that no two payments will have the same ID, without the generating party needing to check against a central database to see if an ID is already in use.

• It is highly recommended that the UETR should be generated and assigned by the Source PSP, so that there is full end-to-end traceability of this payment using the UETR.

• However, if the domestic format does not cater for UETR, the Source IPS must generate a UETR upon translating a domestic-format payment instruction into the Nexus pacs.008. The IPS must be able to correlate the generated UETR back to the payment instruction received from the Source PSP.

• The UETR must be carried unaltered throughout the payment life cycle. The UETR must be included in each transaction according to the Nexus Usage Guidelines.

• The same UETR must be included in any pacs.002 reject or confirmation messages sent in response to the pacs.008, and any subsequent return messages that need to reference the original pacs.008.

Other Reference Elements

Other reference elements must be transported unaltered in accordance with the Nexus Usage Guidelines:

• Instruction ID (in Credit Transfer Transaction Information)

  • The instruction identification is a point-to-point reference that can be used between the instructing party and the instructed party to refer to the individual instruction. It can be included in several messages related to the instruction. In accordance with the CPMI ISO 20022 harmonisation requirements, this is not required in Nexus (despite being mandatory in CBPR+).

• End-to-End ID (in Credit Transfer Transaction Information)

  • Unique identification, as assigned by the initiating party, to unambiguously identify the transaction. If provided, this identification must be passed on, unchanged, throughout the entire end-to-end chain.

• Transaction ID (in Credit Transfer Transaction Information)

  • Unique identification, as assigned by the first instructing agent, to unambiguously identify the transaction. If provided, this identification must be passed on, unchanged, throughout the entire interbank chain.

• Clearing System Reference (in Credit Transfer Transaction Information)

  • Unique reference, as assigned by a clearing system, to unambiguously identify the instruction. If provided, this identification must be passed on, unchanged, throughout the entire interbank chain.