# Update User Complaint
source: https://developer.mastercard.com/india-online-dispute-resolution/documentation/use-cases/update_dispute/index.md

The Update User Complaint API updates the user complaint details based on the complaint tracking number. Issuers and acquirers can use this API.

## Prerequisites {#prerequisites}

The issuer or acquirer needs the following parameters:

* Complaint tracking number
* Comment
* Complaint status (optional)

<br />

When new or corrected information becomes available for a customer's existing complaint, the issuer or acquirer updates the record rather than creating a new one. The Update User Complaint API (`PUT /complaints`) applies the change using the complaint tracking number.

API Reference: `PUT /complaints`

## Sequence Diagram {#sequence-diagram}

Diagram update-dispute-by-tracking-number

### Execution steps {#execution-steps}

1. The user sends a valid tracking number and comments to IODR. Note: Sending a complaint status is optional.
2. The IODR validates the tracking number and status, ensuring the comment is no more than 250 characters.
3. If the tracking number is invalid, the IODR responds with an error message.
4. If any of the fields is valid and exists, the IODR sends the updated status and success message to the user.

Note: IODR sends email updates about complaints to the issuer and acquirer.

## Complaint status values {#complaint-status-values}

The `complaintStatus` field is optional, but when supplied it must be one of the values below. The values you are allowed to set depend on **who you are** --- the issuer and the acquirer can set different statuses.

### Statuses the issuer can set {#statuses-the-issuer-can-set}

|         Value         |                   Plain-language meaning                    |
|-----------------------|-------------------------------------------------------------|
| `UNDER_INVESTIGATION` | The issuer is actively reviewing the dispute.               |
| `SENT_TO_ACQUIRER`    | The dispute has been routed to the acquirer for a response. |
| `RESOLVED`            | The dispute has been resolved and closed.                   |
| `REJECTED`            | The dispute has been rejected and closed.                   |

### Statuses the acquirer can set {#statuses-the-acquirer-can-set}

|         Value         |                    Plain-language meaning                     |
|-----------------------|---------------------------------------------------------------|
| `UNDER_INVESTIGATION` | The acquirer is actively reviewing the dispute.               |
| `CLEARING_DONE`       | Clearing (settlement) for the transaction has been completed. |
| `REVERSAL_DONE`       | A reversal (refund) for the transaction has been completed.   |
| `CLEARING_TO_FOLLOW`  | Clearing has not happened yet but is expected to follow.      |
| `REVERSAL_TO_FOLLOW`  | A reversal has not happened yet but is expected to follow.    |

## Error Resolution {#error-resolution}

For details on error resolution, refer to the [Code and Formats](https://developer.mastercard.com/india-online-dispute-resolution/documentation/code-and-formats/index.md) section.