Build a custom credit card payments extension

In this tutorial, you'll learn how to do the following tasks:

• Create a Checkout UI extension
• Create a custom credit card payments extension
• Explore the payment, refund, void, reject and capture session flows, and how to implement them yourself
• Submit your payments extension for review

• Install Shopify CLI
• Create a Shopify Partner account and apply to become a payments partner
• Create a development store
• Create an encryption certificate

To build a custom credit card payment extension you will need to create a new app, with a custom credit card payments extension and Checkout UI extension correctly applied.

Create your new app using the Shopify CLI. As a first step, we recommend deploying a skeleton app to establish a base for customization.

After creating your app, generate a Checkout UI extension and deploy your app to Shopify. This extension will be used to collect additional information that's required to process a payment.

1. Use the Shopify CLI to scaffold a Checkout UI extension for your app.
2. Name your extension and choose to work in TypeScript React.

1. After you generate the extension, deploy your app to Shopify Partners. This will allow you to link the Checkout UI extension with your payments app extension in the next section.
2. Navigate to your app in Shopify Partners (Apps > Your App).
3. Click Extensions. At this point, you should see the Checkout UI extension you created and released.

Your Shopify app becomes a payments app after you've created and configured your payments extension.

1. Run the following command to start generating your payment extension:

2. When prompted, choose your organization & create this as a new app

3. When prompted for "Type of extension", select "Payments App Extension > Custom Credit Card" and name your extension

1. Disable embedding

   Shopify apps are embedded by default, but payments apps are an exception to this, because they don't need to render anything in Shopify admin. In shopify.app.toml, update the embedded and set it to false.

2. Push the configuration changes to your app and start your server

   In a terminal, run the following commands to push the configuration changes to your app:

• Install the packages required to run the payments app:

• Deploy your app to update the config, which is defined in shopify.app.toml:

1. Start your development server

   To run the app locally, start your development server:

   1. You might be prompted to log in to your Partner account.

      In your terminal, select your development store. You can use the generated URL to test your payments app by using it in your payments app configuration. If you want a consistent tunnel URL, then you can use the --tunnel-url flag with your own tunnel when starting your server.

   2. Press p to open the app in your browser. This brings you to your development store's admin, where you can install your payments app.

Configuration of custom credit card payments extension is similar to a Credit Card payments extension.

Your payments extension configures the following fields:

The UI extension generated in Create a Checkout UI extension will determine what fields, validation, and form submission behavior is presented to buyers during checkout.

This is where you would identify the checkout extension you built prior to creating your payment app extension to tie them into one another.

The fields you are looking to accept from your UI extensions so the payment method can validate the correct data is sent from the front end.

The above field definitions would be defined for something that looks like this:

The above field definitions would be defined for something that looks like this:

After you've finished your draft, you can submit your payments extension for review. You can use this same process to submit new versions of your payments extension. Any changes that are made after publishing need to be approved by Shopify as a new version of the payments extension.

To get your extension ready for review, you can create and release an app version with the deploy command.

1. Navigate to your app directory.

2. Run the following command.

An app version created using Shopify CLI contains the following:

• The app configuration from the local configuration file. If the include_config_on_deploy flag is not set or false, the configuration from the active app version will be used instead.

• The local version of the app's CLI-managed extensions. If you have an extension in your deployed app, but the extension code doesn't exist locally, then the extension isn't included in your app version.

• The latest drafts of dashboard-managed extensions.

Releasing an app version replaces the current active version that's served to stores with your app installed. It might take several minutes for app users to be upgraded to the new version.

Payments apps are reviewed by Shopify to ensure that they provide great merchant experience. Follow these steps to submit your app version for review:

1. From the Partner Dashboard, go to Apps.

2. Select your app from the list.

3. Click Versions.

4. Select the version that you want to release.

5. Click Submit for review.

After Shopify has reviewed and approved the app version you can release it to merchants.

1. From the Partner Dashboard, go to Apps.

2. Click Release to release the new app version to users.

Once this version has been released, follow these steps to install your app on your development store:

1. From the app splash page, enter an account name.

2. Select Ready > Unstable and click Submit.

3. In the banner, click Return to Shopify.

4. Enable test mode.

5. Click Activate.

6. You can select Resolve to complete the payment, or Reject to cancel and go back.

The Payments App functions similarly to the Credit Card payment method, allowing you to gather additional information from the buyer at the outset to facilitate payment processing. The primary distinction is that Checkout UI extension data is included in the start_payment_session body.

Outlined below is a comprehensive diagram depicting the potential flow for processing a custom credit card payment. It's important to note that the pending state is optional; you can directly proceed to either resolve or reject the payment if there is no need to place it in a pending state. For further details on processing credit card payments, please refer to this resource.

Once we start the payment session with your payments app, that initiation will also contain the metadata in a shape similar to what was specified within the field definitions. A sample payment session payload of what is to be expected can be seen below.

Payments with payments apps are processed asynchronously. When the buyer completes their checkout, a request will be sent from Shopify to the Payment session URL defined in Configure your payments app extension, with the checkout and payment details. The Payments app should respond with HTTP 2xx to indicate that the payment session was started, and should begin processing the custom credit card payment at this point.

The new metadata we are passing through payment session would be contained within the payment_method request params under attributes:

Once the payments app has responded to the initial start payment session request, it should begin processing the payment. Since this is an asynchronous process, the payments app will be performing the next step independently, through the paymentSessionResolve mutation on the Payments Apps GraphQL API. This mutation will resolve the payment session, indicating that the payment was successful.

Example GraphQL mutation:

After this, the payment will be marked as resolved in Shopify.

If a payment was unsuccessful for any reason, the payments app must use the paymentSessionReject mutation.

These are the reasons you can reject a payment session with.

The refund flow begins with an HTTP POST request sent from Shopify to the payments app's refund session URL. Shopify must receive an HTTP 201 (Created) response for the refund session creation to be successful. You can read more about refund sessions and how to reject or resolve refund sessions here.

Example request body:

After the app has successfully processed the refund request, it's resolved by using the refundSessionResolve mutation. The id argument corresponds to the gid of the refund.

Example GraphQL mutation:

After this, the refund will be marked as resolved in Shopify.

If the app can't process a refund, then it needs to reject it. You should only reject a refund in the case of final and irrecoverable errors. Otherwise, you can attempt to process the refund again.

The refund is rejected using the refundSessionReject mutation.

As part of the rejection, a reason why the refund was rejected must be included as part of RefundSessionRejectionReasonInput.

Example GraphQL mutation:

A capture can only be performed when the payment initiated by Shopify has a kind property with a value of authorization. With an authorization, the app places a hold on funds and then replies to Shopify's capture request.

The capture flow begins with an HTTP POST request sent from Shopify to the payments app's capture session URL. You can read more about capture sessions and how to reject or resolve capture sessions here.

Example request body:

After the app has successfully processed the capture request from Shopify, it's resolved using the captureSessionResolve mutation on the Payments Apps GraphQL API.

Example GraphQL mutation:

After this, the capture will be marked as resolved in Shopify.

If you don't want to process a capture request, then you should reject it. You might want to reject a capture if authorization has expired or if you suspect that the request is fraudulent or high risk. You should only reject a capture in the case of final and irrecoverable errors. Otherwise, you should re-attempt to resolve the capture.

The app rejects a capture using the captureSessionReject mutation.

As part of the rejection, you need to include a reason why the capture was rejected as part of CaptureSessionRejectionReasonInput.

Example GraphQL mutation:

A void can only be performed when the payment initiated by Shopify has a kind property with a value of authorization.

The void flow begins with an HTTP POST request sent from Shopify to the payments app's void session URL. You can read more about void sessions and how to reject or resolve void sessions here.

Example request body:

After the app has successfully processed the void request, it is resolved using the voidSessionResolve mutation on the Payments Apps GraphQL API.

Example GraphQL mutation:

After this, the void will be marked as resolved in Shopify.

If your app can't process a void request, then you should reject it. You should only reject a void in the case of final and irrecoverable errors. Otherwise, you can attempt to resolve the void again.

You can reject a void using the voidSessionReject mutation. As part of the rejection, you need to include a reason why the void was rejected as part of VoidSessionRejectionReasonInput.

Example GraphQL mutation:

Note: Please ensure you have the latest version of checkout-ui-extensions-react, as well as the latest version of checkout-ui-extensions as the default package installation will ship with a versions that do not contain useApplyPaymentMethodAttributesChange, as well as PaymentMethodAttributesUpdateChange.

Here is a sample of what a checkout UI extension could look like for a Custom Credit Card Payment Method payments app (this would be within your Checkout.tsx file of your checkout UI extension):

As we are still building some features. There are currently some limitations within the system that we're still working on. They are as follows:

• App deployments from the partners UI dashboard only pickup checkout UI extensions if they have previously been deployed & released. If you want to use the partner dashboard UI to deploy new versions of your app. Make sure you have previously deployed & released the corresponding checkout UI extension from the CLI first.

1. Does the custom credit card extension accommodate split payments or installments?

   Custom credit card extension provides partners with the flexibility to include a field in the extension, showcasing various payment options to buyers. However, it's important to note that Shopify processes these as a single, full payment to the processor. Any arrangements for payment schedules or installments are then managed directly between the processor and the buyer, without Shopify's involvement.

Congratulations! You set up a custom credit card payments app.