Adding Open Banking (Checkout mode) 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.


To add Open Banking to your payment page you will need to carry out the following steps:

  1. Retrieve your API Key - contact our Client Support team if you do not have a key.
  2. Generate a unique Payment ID.
  3. Include a reference to a CSS and JS file on your payment page.
  4. Add a button to your page.
  5. Add a JavaScript Event Listener to detect when the payment UI pop-up window closes.


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.

Generating a Unique Payment ID

Each Open Banking payment requires a unique payment identifier.

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:

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. The user selects the ASPSP (i.e. the bank) in which his account is held (Barclays for example) and clicks Continue.
  5. A confirmation of the bank selected is displayed and the user clicks Confirm.
  6. The user is then redirected to his bank where he must sign on with his online banking credentials:
  7. Once successfully signed on the user can choose to Confirm the payment to the merchant:
  8. The payment is authorised and the payer (PSU) is redirected to the Nuapay TPP with a confirmation message:
  9. The pop-up window may be closed by the payer (or may close automatically) and the user is redirected to the merchant payment page, with a confirmation message.
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).