Payment Initiation Service Provider Checkout Page implementation Options for Partners
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Your PISP checkout page may be implemented in one of the following ways:

  1. CHECKOUT
  2. SELF_HOSTED
  3. SELF_HOSTED_CALLBACK
Checkout This mode lets you use the Nuapay user interface for Bank Selection. You process JavaScript events to determine when the payment flow is completed.
Self-Hosted The user interface is handled by you, the merchant (or partner, acting on behalf of a merchant) for Bank Selection; callback handling is through the Nuapay TPP, you process the merchantPostAuth on your system when the payment flow is completed.
Self-Hosted-Callback In this mode the user interface is handled by you, the merchant (or partner, acting on behalf of a merchant) and you manage the PSU’s experience after interacting with an ASPSP: the Callback bypasses the Nuapay TPP, you manage the callback URL that is required for each ASPSP interaction, upon receiving the callback you send the details back to Nuapay for processing.

What is the Best Approach?

Each approach has its advantages and disadvantages - the table below summarises the different implementations

Mode Advantages Disadvantages
Checkout Easier implementation; No bespoke UI design (e.g. for the Bank Selection screen) is required; No TPP license is required. No UI customisation is possible; “Powered by Nuapay” is displayed on the UI.
Self-Hosted Full control over the user interface Requires more development effort; Requires a call to the List Bank service; following the PSU’s interaction on the selected ASPSP, the Callback URL redirects the user to the Nuapay TPP.
Self-Hosted-Callback Full control over the user interface and the Callback URL; it is possible to bypass the Nuapay TPP application Requires additional development effort; Requires a call to the List Bank service; Registration of the callback URL (via Software Statement Assertions in the UK Open Banking scheme, for example) at each ASPSP is required.

Checkout Mode

In Checkout mode (for Partners) you will:

  1. Use your partner-level API key to retrieve the list of your merchants and retrieve a token representing the required merchant.
  2. Call the /payments endpoint on behalf of your merchant, using the OAuth token retrieved in the previous step (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. Process the callback URL; display the status to the PSU and close the TPP UI, passing control to the parent window.
  6. Use Retrieve Payment to determine the final payment status, if required (an optional step).

A detailed overview of the various steps involved in this flow is provided in the image below.

Checkout Flow - Partner
CHECKOUT Flow - Partner

For more on this see Checkout Payment Page Setup.

Self-Hosted Mode

In Self-Hosted mode (for Partners):

  1. Use your partner-level API key to retrieve the list of your merchants and retrieve a token representing the required merchant.
  2. You will design your own Bank Selection screen; use Retrieve Banks to populate your interface.
  3. Once the payer has selected a bank, call the /payments endpoint using the OAUth token, representing the required merchant, (see Create Payment). Set the integrationType to SELF_HOSTED, specify the bankId provided by the payer and set the merchantPostAuthUrl.
  4. Redirect the PSU to the ASPSP to authorise the payment. The callbackUrl is hard-coded for the Nuapay TPP.
  5. Process the callback URL to the configured merchantPostAuthUrl.
  6. Use Retrieve Payment to determine the final payment status, if required (an optional step).

A detailed overview of the various steps involved in this flow is provided in the image below.

Self-Hosted Flow
SELF_HOSTED Partner Flow

For more on this see Self-Hosted Payment Page Setup

Self-Hosted-Callback Mode

In Self-Hosted-Callback mode:

  1. Using your partner-level API key retrieve the list of your merchants and retrieve a token representing the required merchant.
  2. You will design your own Bank Selection screen; use Retrieve Banks to populate your interface.
  3. Once the payer has selected a bank, call the /payments endpoint using the OAUth token, representing the required merchant, (see Create Payment). Set the integrationType to SELF_HOSTED_CALLBACK, specify the bankId provided by the payer and set the merchantPostAuthUrl.
  4. Redirect the PSU to the ASPSP to authorise the payment - note that in this mode the callbackUrl = the merchantPostAuthUrl.
    • Unlike in the SELF_HOSTED mode, the OAuth callback from the bank is not passed to the Nuapay TPP directly, instead it is directed to the merchantPostAuthUrl.
    • The partner retrieves An OAuth token.
    • The payment callback is passed to the Nuapay TPP.
  5. Process the callback and confirm the payment status.
  6. Use Retrieve Payment to determine the final payment status, if required (an optional step).

A detailed overview of the various steps involved in this flow is provided in the image below.

Self-Hosted-Callback Partner Flow
SELF_HOSTED_CALLBACK Partner Flow