> For the complete documentation index, see [llms.txt](https://docs.nexusglobalpayments.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nexusglobalpayments.org/payment-setup/step-13-16-set-up-and-send-the-payment-instruction.md).

# Step 13-14: Set up and send the payment instruction

Now that the Sender has approved the payment, the PSP must set up the Nexus-standard `pacs.008` payment instruction (or domestic equivalent) and submit it to the local IPS.

## Step 13: Construct the Nexus pacs.008 payment instruction <a href="#toc116457924" id="toc116457924"></a>

1. **The PSP constructs the pacs.008 payment instruction:** this will make use of information from the earlier responses to:
   1. `GET /quotes`
   2. The `acmt.023` proxy or account resolution request
2. The Source PSP should define whether the payment is to be sent as a normal priority payment (to be used for P2P payments) or a high priority payment (intended for P2M payments) by setting the Instruction Priority (`/Document/FIToFICstmrCdtTrf/CdtTrfTxInf/PmtTpInf/InstrPrty/`) as follows:
   1. **`NORM`**: This is the default option. Nexus will wait on the response from the Destination IPS before confirming (or rejecting) to the Source IPS. This is the option that is supported by all IPSOs. Payments will be processed instantly, but in case of technical issues, the Destination IPSO maintains the final state of the payment.
   2. **`HIGH`**: This is the option for urgent payments and physical point-of-sale payments (eg where the customer cannot leave the store until the payment is confirmed). If `HIGH` is used, Nexus will monitor the end-to-end processing time of the payment and will proactively reject the transaction in case no response is received in time from the Destination IPS. This will ensure the payment achieves a final status within the Maximum Execution Time at all times but may lead to a slightly higher number of rejects. Not all IPSOs will be able to support high-priority payments. Whether the Destination IPS supports high-priority payments is part of the GET countries API response.

See [MESSAGE: pacs.008 FI to FI Customer Credit Transfer](/messaging-and-translation/message-pacs.008-fi-to-fi-customer-credit-transfer.md) for further details.

## Step 14: Send the `pacs.008` to the Source IPS <a href="#toc116457927" id="toc116457927"></a>

1. Once the Sender has confirmed the payment, the PSP should submit the `pacs.008` payment instruction to the Source IPS (using the same secure connection that the PSP normally use to submit domestic payment instructions to the IPS).
2. The Source IPS will process the payment and then forward it to Nexus, following the process in [Payment Processing](/payment-processing/key-points.md).

{% hint style="warning" %}
**Checking for duplicated or fraudulent payments**

* In general, Nexus expects the Source PSP to ensure that any payment instructions it sends to Nexus are legitimate, non-fraudulent and compliant with all applicable regulations, and should therefore be processed. It is therefore the responsibility of the Source PSP to defend against sending fraudulent payments or payments that were sent in error.
* Nexus uses the **UETR (Unique End-to-End Transaction Reference)** to check whether a payment is unique. Nexus will check whether a payment with the same UETR has already been processed and will not process duplicates.
* However, Nexus will not check whether similar payments with different UETRs are possible duplicates. For example, if a Source PSP sends two payments, for the exact same amount, between the same sender and recipient accounts, but with different UETRs, Nexus will assume both payments are intentional and will process both.
  {% endhint %}