Accept Bancontact with UI components

Use Unzer UI component to add Unzer Bancontact payment to your checkout page.


Using UI components for Bancontact, you create a payment type resource that will be used to make the payment. You do not need any form fields for this payment method. You can check a demo version of the component here. The basic steps for integrating using UI components are the same for all payment methods, and you can read about them here.

Before you begin

Step 1: Add UI components to your payment page
client side

First, you need to initiate our UI components library and add the payment form to your payment page.

Initiate UI component

Load our JS script and CSS stylesheet

Include Unzer’s script and stylesheet on your website.

Always load the script and stylesheet directly from https://static.unzer.com:

<link rel="stylesheet" href="https://static.unzer.com/v1/unzer.css" />
<script type="text/javascript" src="https://static.unzer.com/v1/unzer.js"></script>
Faster load time
To make your website load faster, insert js scripts at the bottom of your HTML document.
Importing Unzer styles
To minimize the risk of Unzer styles affecting the styles of your webpage we suggest putting unzer.css on top of other imported CSS files.

Create an Unzer instance

Create an unzer instance with your public key:

// Creating an unzer instance with your public key
var unzerInstance = new unzer('s-pub-xxxxxxxxxx');
Placeholder keys
In the example above, we used a placeholder API key for example purposes. You should replace it with your public key.

Localization and languages

We support localization with locale option parameters. Please check the Localization page on supported locales.

The auto option (which is applied by default) uses the client’s browser language.

Here you can see how to set the language, in our case ‘de-DE’ - to do so add a comma separated parameter to your unzer instance:

// Creating an unzer instance with your public key
var unzerInstance = new unzer('s-pub-xxxxxxxxxx', {locale: 'de-DE'});

Implement the payment form

To securely collect payment data from your customer, you need to create a payment form with empty DOM elements, and unique ID’s within them. That way, unzer.js will know where to place its UI components.

<form id="payment-form" class="unzerUI form" novalidate>
    <div id="bancontact-holder" class="field"></div>
    <button class="unzerUI primary button fluid" id="submit-button" type="submit">Pay</button>
<form id="payment-form" class="unzerUI form" novalidate>
    <button class="unzerUI primary button fluid" id="submit-button" type="submit">Pay</button>

Matching IDs

When choosing your ID for a UI component, be sure the names in your HTML and javascript match.

For example:

<div id="example-bancontact"> matches containerId: "example-bancontact".

Create a Payment Type resource

Call the method unzerInstance.Bancontact() to create an instance of the payment type Bancontact.

// Creating an bancontact instance
var bancontact = unzerInstance.Bancontact()

// Rendering input field
bancontact.create('holder', {
  containerId: 'bancontact-holder'
// Creating an bancontact instance
var bancontact = unzerInstance.Bancontact()

Add an event listener for “submit” of the form.

Inside, create a Promise on the invoiceSecured object. The Promise is either resolved or rejected:

let form = document.getElementById('payment-form');
form.addEventListener('submit', function(event) {

        .then(function(result) {
            // Submit the id of the created payment type to your
            // backend to perform the payment transaction with it.
            typeId = result.id;
        .catch(function(error) {
            // handle errors

Optional: Customize UI Components

You can easily customize the font of the forms by changing the options within the create method. Here you can set the following styles: fontSize, fontColor and fontFamily.

bancontact.create('holder', {
    containerId: 'bancontact-holder',
    fontSize: '16px',
    fontColor: 'lightgrey',
    fontFamily: 'Arial,
    Helvetica, sans-serif'

Step 2: Make a payment
server side

Make a Charge transaction

Now, make a charge transaction with the Bancontact typeId that you created and the returnUrl leading back to your shop after the payment is finished on the external page. With the charge transaction, an amount is requested but is not yet transferred. Initially, the transaction will be pending, and a payment resource is created.

POST https://api.unzer.com/v1/payments/charges
  "amount" : "20",
  "currency": "EUR",
  "returnUrl": "https://www.my-shop-url.de/returnhandler",
  "resources" : {
    "typeId" : "s-bct-jldsmlmiprwe"
$unzer = new Unzer('s-priv-xxxxxxxxxx');
$bancontact = $unzer->fetchPaymentType('s-bct-0ajzmaxcuvhc');
$charge = $bancontact->charge(20.0, 'EUR', 'https://www.my-shop-url.de/returnhandler');

Unzer unzer = new Unzer("s-priv-xxxxxxxxxx");
Charge charge = unzer.charge(BigDecimal.ONE, Currency.getInstance("EUR"), "s-bct-0ajzmaxcuvhc", new URL("https://www.my-shop-url.de/returnhandler"));

The response looks similar to the following example:

    "id": "s-chg-1",
    "isSuccess": false,
    "isPending": true,
    "isError": false,
    "redirectUrl": "https://stg-payment.unzer.com/v1/redirect/bancontact/s-sGYdGywWpxzW",
    "message": {
        "code": "COR.000.100.112",
        "merchant": "Request successfully processed in 'Merchant in Connector Test Mode'",
        "customer": "Your payments have been successfully processed in sandbox mode."
    "amount": "20.0000",
    "currency": "EUR",
    "returnUrl": "https://www.my-shop-url.de/returnhandler",
    "date": "2021-05-10 00:51:03",
    "resources": {
        "paymentId": "s-pay-131937",
        "traceId": "70ddf3152a798c554d9751a6d77812ae",
        "typeId": "s-bct-jldsmlmiprwe"
    "paymentReference": "",
    "processing": {
        "uniqueId": "31HA07BC8157BD2BC04D483EFA914465",
        "shortId": "4845.3426.1987",
        "traceId": "70ddf3152a798c554d9751a6d77812ae"

For a full description of the charge transaction, refer to the relevant server-side integration documentation page: Charge a payment (direct API calls), Charge a payment (PHP SDK), Charge a payment (Java SDK).

Forward the customer to external payment page

After you charge the Bancontact resource, implement the following flow:

  1. Forward the customer to the redirectUrl returned in response to your charge request.
  2. The customer is forwarded to the Bancontact payment page.
  3. After a successful payment or abort on the Bancontact page, the customer is redirected to the returnURL specified in the initial charge call.

Step 3: Check status of payment
server side

Once the customer is redirected to the returnUrl, you can fetch the payment details from the API, by using the resources.paymentId from the Charge response above to handle the payment according to its status. If the status of the payment is completed , the payment process has been finished successfully and can be considered as paid. Check all possible payment states here.

GET https://api.unzer.com/v1/payments/{resource_ID}>/charges/{transaction_ID}

    "id": "s-pay-xxxxxx",
    "state": {
        "id": 1,
        "name": "completed"
    "amount": {
        "total": "20.0000",
        "charged": "20.0000",
        "canceled": "0.0000",
        "remaining": "0.0000"
    "currency": "EUR",
    "orderId": "",
    "invoiceId": "",
    "resources": {
        "customerId": "",
        "paymentId": "s-pay-131937",
        "basketId": "",
        "metadataId": "",
        "payPageId": "",
        "traceId": "70ddf3152a798c554d9751a6d77812ae",
        "typeId": "s-bct-xxxxxxxxx"
    "transactions": [
            "date": "2021-05-10 00:51:03",
            "type": "charge",
            "status": "success",
            "url": "https://api.unzer.com/v1/payments/s-pay-xxxxxxx/charges/s-chg-1",
            "amount": "20.0000"

Step 4: Display the payment result
client side

Use the information from the Check status of payment step to show payment result to your customer.
This can be the success or error page of your shop. If something went wrong you can use the client message from the API response and show it to the customer.

Manage payment
server side

For more details on managing Bancontact payments, see Manage Bancontact payments


We recommend subscribing to the payment event to receive notifications about any changes to the payment resource. As soon as the event is triggered you should fetch the payment and update the order status in your shop according to its status.


For more details on implementing Webhooks to receive notifications, see Notifications.

Error handling

All requests to the API can result in an error that should be handled. Refer to the Error handling guide to learn more about Unzer API (and other) errors and handling them.

Test & go live

You should always test your integration before going live. First perform test transactions using test data. Next, check against Integration checklist and Go-live checklist to make sure the integration is complete and you’re ready to go live.

See also