# Create Pre-Authorization Service

## Overview

The pre-authorization flow is exactly the same as the payment flow. To allow the customer to perform the
purchase through a pre-authorization, just send the value **"preauthorization"** on the **transaction_type** field. [Learn more.](pagamento-html-begin.md)

> **Attention:**
>
>The pre-authorization has one restriction when compared to the payment flow. The authorizer, the number and type of installments are **mandatory for the transaction creation** and must be prefixed by the merchant, **not allowing the customer to alter or choose another value**.
>
>The fields used are, respectively: **authorizer_id**, **installments** and **installment_type**. They are described in the [transaction creation process request parameters](pagamento-html-begin.md#request-parameters).

## Pre-Authorization request example

```
{
    "merchant_id": "codigoDaLoja",
    "amount": "1800",
    "transaction_type":"preauthorization",
    "authorizer_id": "1",
    "installments": "3",
    "installment_type": "4"
}
```

## Pre-Authorization capture

When a pre-authorization is confirmed successfully, the merchant can capture it later via web services, thus effecting the billing. [Learn more.](pre-autorizacao-rest-capture.md)