# VUK 507 Services

### Overview

VUK 507 services cover standard transactions performed via physical POS devices, including sales, refunds, voids, and end-of-day operations.

This structure operates independently of e-invoice processes and is based on the traditional POS payment flow.

### Scope

The following operations are covered in this section:

* Payment (Sale)
* Refund
* Void
* Transaction Query
* Refundable Transaction Information
* Partial Payment
* End of Day

### Authentication

OAuth2-based authentication is used for all service calls.

> Authorization: Bearer {access\_token}\
> Content-Type: application/json

{% hint style="warning" %}
Note: The access token is obtained during the Login step and is mandatory for all service requests.
{% endhint %}

### Genel Ödeme Akışı

```mermaid
sequenceDiagram
    autonumber
    participant CashRegister as Sales Application
    participant Iyzico as iyzico Terminal API
    participant GMU as GMU Device
    participant Bank as Bank / Acquirer

    CashRegister->>Iyzico: POST /v2/terminal-host/gmu/payment
    Note right of CashRegister: Authorization Bearer access_token
    Iyzico->>GMU: Forwards the sale request
    GMU->>Bank: Initiates payment authorization
    Bank-->>GMU: Transaction result
    GMU-->>Iyzico: Payment result and transaction details
    Iyzico-->>CashRegister: Returns sale response

    alt Transaction successful
        Note over CashRegister,Iyzico: paymentId, authCode, hostReference are returned
    else Transaction failed
        Note over CashRegister,Iyzico: status failure, errorCode, errorMessage are returned
    end
```


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