Adding Open Banking (Checkout mode for a Merchant Integration) as a payment option to your Payment Page requires a little configuration as outlined below. In Checkout mode you will use the Nuapay user interface for Bank Selection and Confirmation screens.
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A detailed overview of the various steps involved in the Checkout flow is provided in the image below.

Checkout Flow - Merchant
CHECKOUT Flow - Merchant

In Checkout mode you will:

  1. (Optionally) Use your API key to retrieve a merchant access token. (For more on this see retrieving tokens).
  2. Call the /payments endpoint, using the OAuth token retrieved in the previous step (or else use your API Key) (see Create Payment) and set the integrationType to CHECKOUT. Manage the returned payment identifier with some Nuapay-provided JS and CSS to render the Bank Selection screen for your payers.
  3. The PSU selects a bank.
  4. Redirect the PSU to the ASPSP to authorise the payment.
  5. The Nuapay TPP posts the payment ID to the partner/merchant URL (merchantPostAuthUrl).
  6. Use Retrieve Payment to determine the final payment status, if required (an optional step).


An API Key or OAuth token uniquely identifies you on Nuapay and is required to allow you to use our API services.

For more on API Keys and OAuth, see the API Basics section.

Calling the Payment Endpoint

The Open Banking payment endpoint returns a payment identifier on a successful invocation.

To generate a payment ID:

  1. Generate a server-to-server call to /payments.
  2. Ensure that you have referenced your API Key or OAuth token in the request.
  3. The /payments service is described in Create Payment.

Adding the CSS and JS File References

On your payment page you will need to add the following:

For Sandbox

<script src=""></script>
<link rel="stylesheet" type="text/css" href="" />

For Production

<script src=""></script>
<link rel="stylesheet" type="text/css" href="" />

Adding The Open Banking Pay Button

At this point you have:

  • Added the JS and CSS links to your payment page.
  • Retrieved the payment ID (via the Create Payment service).

To enable the PAY button you will need to add an onclick event. See the example below:

<a class="btn btn-primary" href="#" onclick="NuapayOpenBanking.showUI(‘gabxrlvbl5’;‘’);">Pay Now</a>

This button will open the Select Banks pop-up for the Payment ID gabxrlvbl5 is the location of the Nuapay TPP User Interface, which will allow your customers to select their bank.

Note that there is a Sandbox and Production TPP for this so you will need to specify the correct URL based on whether you are testing or working in Production:


Adding a Listener

Once you have successfully added the PAY button to your site you will next need to handle when the pop-up window is closed. In a successful flow:

  • The pop-up will be closed by users after they confirm the payment with their bank and are redirected to your confirmation message.
  • Users may also choose to cancel out of the flow at any point and close the pop-up window without completing the payment.

To manage the closing of the pop-up window, you will need to add a Listener to your parent Payment Page window to listen for the close event, which (for Payment ID gabxrlvbl5) would look like this:

{"status":"CLOSED","paymentId":" gabxrlvbl5"}

A Sample Listener is provided below.


var listener = function(event) {
    if("CLOSED") {
        var url = "/merchant/status?id=" +;
          url: url,
          success: function(data){
            if (data.status == "COMPLETE") {
            } else {
          error: function(){



Here we are checking that the event is a closed event, in this example the merchant is calling back to their own server.

The call is to /merchant/status?id=gabxrlvbl5

The End-User Experience

Once configured, your users’ interaction with Open Banking payments will be similar to the following for a Desktop user (for users on mobile devices, the screens vary from the sample presented below):

The PSU (i.e. the end user) will select the required goods or services on your merchant site and:

  1. Select Nuapay Open Banking as the payment method.
  2. Click Pay.
  3. A pop-up window overlayed on the calling payment page is generated. This is rendered through Nuapay’s TPP application:
  4. If required, the PSU can click the order details icon to expand and view the items making up the order:

    (See the orderDetails object on the Create Payment endpoint for more on this).
  5. The user selects the ASPSP in which his/her account is held (Revolut for example) and is redirected to the bank’s logon page (or optionally the PSU selects the bank and clicks Continue, if you have decided to configure a Confirmation page - see the following section for more on this).
  6. The user then authenticates on to the selected ASPSP (Revolut in this example):
  7. Once authenticated with the bank, the user can choose to Authorise the payment:
  8. Once authorised, the PSU is redirected to the Nuapay TPP with a confirmation message:
  9. The pop-up closes (either the user clicks Close or it closes automatically after 30 seconds) and the user is redirected to the merchant payment page, with a confirmation message.

Configuring a Confirmation Screen

Some merchants like the Open Banking payment user experience to be as fast as possible:

The PSU:

  1. Selects the required ASPSP.
  2. Logs on to his/her bank.
  3. Authorises the payment and is redirected to a success page.

Friction is limited and the user can completed the payment in seconds.

However in some cases a little friction isn’t all bad! Especially where users may be new to the payment method, it can be good to slow things down a little. With this in mind, rather than provide only the 3 steps above, you can configure the flow to have an additional confirmation page.

With this additional page added:

  1. The PSU selects the required ASPSP.
  2. The selected bank details are then displayed on a confirmation screen:
  3. The user see the payee details (in this example the merchant Men’s Fashion) and can choose to click Continue (to redirect to the selected bank) or Go Back if he/she has made an incorrect selection.

If you think that you would like to include the confirmation screen in your flow, please inform your Account Manager and we will be happy to configure this for you.

On successful completion of this payment flow your customer has provided his/her consent for the payment to be collected for the selected account. The actual funds transfer to your account may happen within a matter of seconds or it may be processed on the following business day. The speed with which funds are transferred to your account is controlled by your customers’ banks and is determined by the default payment scheme they are using. A scheme like SEPA CT Instant (for Euro payments) or Faster Payments (for GBP payments) will result in funds being credited to your account within seconds. Schemes like SEPA CT and BACS Credit will generally take a business day to process. Nuapay uses the Payment Received Webhook to notify you when funds are settled to your Nuapay account (Note: only available if you are using a Nuapay account).