# 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.

{% hint style="warning" %}
Nexus does not provide a message translation service; this must be handled by the IPS.
{% endhint %}

## Possible approaches to translations in a jurisdiction <a href="#toc159257091" id="toc159257091"></a>

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

### Option 1: Enhance & Translate the Domestic Message <a href="#toc159257092" id="toc159257092"></a>

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 <a href="#toc159257093" id="toc159257093"></a>

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 <a href="#toc159257094" id="toc159257094"></a>

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 <a href="#toc159257095" id="toc159257095"></a>

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

| **APPROACH**                                               | **PROS**                                                                                                                                                                                                                                                                                                                                                 | **CONS**                                                                                                                                                                                                  |
| ---------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Option 1:** Full translation of enhanced domestic format | <ul><li>Minimises changes for domestic PSPs, who can continue to use the existing domestic messages</li><li>Translation can be done by the IPSOs, so that individual PSPs do not need to handle translation</li></ul>                                                                                                                                    | <ul><li>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.</li></ul> |
| **Option 2:** Dual formats in parallel                     | <ul><li>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.</li></ul>                                                                                                                                                                                                          | <ul><li>PSPs need to support two message types and apply logic to understand which type of message to send depending on the type of payment</li></ul>                                                     |
| **Option 3:** Full migration                               | <ul><li>Supports move to standardized ISO 20022 messages rather than bespoke <em>ISO 20022-like</em> messages; aligned with the wider payments industry migration to ISO 20022.</li><li>PSPs who are present in multiple countries only have to support one message type for each function, rather than multiple non-standard domestic formats</li></ul> | <ul><li>Requires a significant domestic change program and testing to manage the migration</li></ul>                                                                                                      |

## Translating the message body <a href="#toc159257096" id="toc159257096"></a>

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** | <p><strong>OUTBOUND</strong><br><em>From</em> <em>Domestic</em> > <em>To Nexus</em></p> | <p><strong>INBOUND</strong><br><em>From Nexus</em> > <em>To Domestic</em></p> |
| ---------------- | --------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| **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.


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