# Reverse a Transaction
source: https://developer.mastercard.com/mastercard-processing-core/documentation/use-cases/transactions-and-fees-management/reverse-a-trans/index.md

## Overview {#overview}

The use case describes how you reverse a posted transaction.

## Sequence diagram {#sequence-diagram}

Diagram reverse-a-trans

### Explanation {#explanation}

1. The server sends a `POST` request to the `/transactions/{transaction_id}/reversal` endpoint.
2. The API returns the HTTP status `201` with the `transactionId` generated by the CMS.

Refer to [Sandbox testing](https://developer.mastercard.com/mastercard-processing-core/documentation/sandbox-testing/transactions-and-fees-management/reverse-a-trans/index.md) for information on how to execute the use case in the Sandbox environment.

## Endpoint {#endpoint}


API Reference: `POST /transactions/{transaction_id}/reversal`