# Investigation & Enquiry
Investigations may be raised in two scenarios:
1. When no `pacs.002` was received to update on the status of a payment
2. When a `pacs.002` status was received, but the customer disagrees with the status.
In the second case, the Source PSP should raise an investigation via the Nexus Service Desk, referencing the UETR of the payment and tagging the Destination PSP.
In the first case, PSPs can resend the pacs.008 using the process below.
#### Investigating when no `pacs.002` payment status report was received
In the scenario where the Source PSP hasn’t received a response after the after the timeout defined in the Nexus Scheme Rulebook, the Source PSP is allowed to request an update by **resending the `pacs.008`**. This is an optional process which can be used by the Sending PSP to retrieve the status of a payment.
Each party must respond to a re-sent `pacs.008` as follows:
* Check if they received the original `pacs.008` payment instruction
* If no `pacs.008` (with those specific Message ID and UETR elements) was received, respond with a `pacs.002` with status `RJCT`, rejecting the payment due to failure in the timestamp validation (\ too far in the past). The specific rejection reason to be used is `TM01`.
* If the original message was received:
* Check whether the party received a corresponding `pacs.002` with a final status (ie status codes `ACCC`, `RJCT`, `BLCK`)
* If yes, resend the `pacs.002` to the Source PSP
* If no, resend the `pacs.008` to the next party in the chain.
This results in the following sequence diagram:
The chain of parties is as follows:
* Source PSP (requestor)
* Source IPS
* Nexus Gateway(s)
* Destination IPS
* Destination PSP
{% hint style="info" %}
In a future release of Nexus, support for the `pacs.028` payment status investigation message will be introduced to support an automated investigation and enquiry process (without needing to resend a `pacs.008`), reducing manual intervention by staff.
{% endhint %}
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