---
title: "Partially refund a balance"
url: "https://docs.adyen.com/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/key-steps-c-library/cancel-or-refund-a-transaction-c-library/partially-refund-a-balance-c-library"
source_url: "https://docs.adyen.com/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/key-steps-c-library/cancel-or-refund-a-transaction-c-library/partially-refund-a-balance-c-library.md"
canonical: "https://docs.adyen.com/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/key-steps-c-library/cancel-or-refund-a-transaction-c-library/partially-refund-a-balance-c-library"
last_modified: "2019-11-13T17:46:00+01:00"
language: "en"
---

# Partially refund a balance

[View source](/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/key-steps-c-library/cancel-or-refund-a-transaction-c-library/partially-refund-a-balance-c-library.md)

## Implement the callback

Implement the callback based on the signature in the** refund\_extern.h** file and pass this as a parameter of the **refund** call. For more information on how to do this, see [Implement callbacks](/point-of-sale/classic-library-deprecation/classic-library-integrations/c-library-integration/calls-and-callbacks-c-library/implement-callbacks).

## Allocate the request struct

Allocates, initializes and returns a `refund_request` struct. Populate the request by performing string duplication.

If you want the data for later use, retain it, or it will be released automatically.

| Name              | Description                                                                                                                                                                                              |
| ----------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `refund_allocate` | Allocates, initializes and returns a `refund_request` struct. Populate the request by performing string duplication.If you want the data for later use, retain it, or it will be released automatically. |

## Call the refund function

Call the `refund` function to initiate a cancel or refund on a transaction that has been processed by the Adyen payments platform. In the refund request, include a `modification_amount_currency` and `m``odification_amount_value` that specifies the amount to be refunded.

### Parameters

| Value             | Description                                                                                                                                                                                     |
| ----------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `refund_request`  | Pointer to the `refund_request` struct, this struct contains all the input parameters for this call.                                                                                            |
| `refund_response` | Pointer to the callback function in the POS that will be called with the results of the `refund` call.                                                                                          |
| `echo_struct`     | Pointer to a POS defined struct. Returned in the callback. It can be used to share a POS data struct between the call to the library and the callback from the library in response to the call. |

## Handle the callback

The `refund_CB` returns the immediate response to the call and a pointer to the POS-defined echo struct.

### Parameters

| Value             | Description                                                                                                                                                                                               |
| ----------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `refund_response` | Pointer to the callback function in the POS that will be called with the results of the `refund` call. If the refund was successful, this struct should should return a result of "**refund-received**".  |
| `echo_struct`     | Pointer to a POS defined struct. Returned in the callback. It can be used to share a POS data struct between the call to the library and the callback from the library in response to the call.           |