Translation To/From Domestic Message Formats

All messages sent to Nexus or sent from Nexus must be in ISO 20022 format and must comply with the relevant Nexus usage guidelines.

However, not all IPSs use ISO 20022 for domestic payments. Where an IPS does not currently use ISO 20022 (or uses another message type or variation from Nexus), it must translate messages to be compliant with the Nexus Usage Guidelines before it sends the message to Nexus.

Nexus does not provide a message translation service; this must be handled by the IPS.

Possible approaches to translations in a jurisdiction

There are three broad approaches to translation, with pros and cons (which are discussed below).

Option 1: Enhance & Translate the Domestic Message

In most cases it will be necessary to enhance the domestic message format to allow it to carry the additional data required for a Nexus message. This additional data includes the Intermediary Agents (Source and Destination SAP), exchange rate, quote ID and (possibly) the UETR.

The IPS would then need to provide a translation service that translates message from the domestic message format to the Nexus message format, and vice versa.

Option 2: Dual formats in parallel

In this case, the IPSO would adapt the IPS and proxy directory to accept Nexus ISO 20022 messages for cross-border proxy resolution, account resolution and payments, while continuing to accept the domestic message format for domestic payments.

The IPSO would adapt its system to also accept pacs.008 requests and generate pacs.002 responses for Nexus cross-border payments. The Proxy Directory Operator would adapt the proxy directory to accept acmt.023 messages and respond with acmt.024.

PSPs who wish to make cross-border payments through Nexus would need to build in support for pacs.008/pacs.002, but could continue to use the domestic messages for domestic payments. PSPs who did not want to make payments through Nexus would not need to support pacs.008/pacs.002.

PSPs who wish to make cross-border proxy or account resolution requests through Nexus would need to build in support for acmt.023/024, but could continue to use the domestic messages for domestic proxy resolutions. PSPs who did not want to make payments through Nexus would not need to support acmt.023/024.

Option 3: Full migration

The IPSO could mandate that all PSPs migrate to using the ISO 20022 messages for both domestic and cross-border proxy resolution, account resolution and payment instructions.

At some point the domestic proxy resolution messages would be retired/disabled. There may be a coexistence period when both message types are accepted.

Pros and cons of different approaches

There are pros and cons of each approach, as outlined below.

APPROACH	PROS	CONS
Option 1: Full translation of enhanced domestic format	Minimises changes for domestic PSPs, who can continue to use the existing domestic messages Translation can be done by the IPSOs, so that individual PSPs do not need to handle translation	Changes may still need to be made to the domestic message to support cross-border proxy resolution. If significant changes are needed, it may be better long-term to consider option 3.
Option 2: Dual formats in parallel	Changes only need to be made by PSPs when they onboard to Nexus, and do not affect PSPs who do not intend to use the service.	PSPs need to support two message types and apply logic to understand which type of message to send depending on the type of payment
Option 3: Full migration	Supports move to standardized ISO 20022 messages rather than bespoke ISO 20022-like messages; aligned with the wider payments industry migration to ISO 20022. PSPs who are present in multiple countries only have to support one message type for each function, rather than multiple non-standard domestic formats	Requires a significant domestic change program and testing to manage the migration

Translating the message body

Each message will have 2 translation points:

• Outbound (from domestic format to Nexus format)

• Inbound (from Nexus format to domestic format)

The table below shows the translation points for each message type currently supported in Nexus:

MESSAGE TYPE	OUTBOUND From Domestic > To Nexus	INBOUND From Nexus > To Domestic
pacs.008	Source IPS > Nexus	Nexus > Destination IPS
pacs.002	Destination IPS > Nexus	Nexus > Source IPS
acmt.023	Source IPS > Nexus	DNexus > Destination IPS
acmt.024	Destination IPS > Nexus	Nexus > Source IPS

For each translation point, the IPSO must define a translation map.