With a previously created payment:customer_not_present scope token, Partners can initiate Klarna payments for subscriptions:

1. The Partner sends a request to the Acquiring Partners to create a Klarna payment session that contains purchase details, customer_token or the token equivalent issued by the Acquiring Partner,interoperability_token and interoperability_data.
2. The Acquiring Partner forwards the required payment context data to Klarna’s Payment Authorization API including:
   1. customer_token
   2. supplementary_purchase_data
      1. subscriptions
   3. step_up_config
   4. request_payment_transaction
3. Klarna returns one of the following responses:
   1. APPROVED – Transaction is completed, proceed to confirmation and store payment_transaction_id.
   2. DECLINED – If the payment is denied, Acquiring Partners have to inform the Partner that the payment could not be completed.

Before calling Klarna’s Payment Authorization API, the Acquiring Partner must ensure their backend accept and forward Klarna specific parameters. These include interoperability parameters that preserve session context as well as supplementary purchase data which improves Klarna’s ability to assess risk, optimize approval rates, and deliver a more personalized checkout experience.

Interoperability parameters

When Partners optimize their integration with Klarna, they are likely to have interoperability parameters to share with the Acquiring Partner.

These ensure consistent customer and transaction context throughout the payment flow and must be forwarded unaltered to Klarna.

Implementation requirements

• Accept the interoperability parameters in the Partner-facing payment request API.
• Forward the interoperability parameters unmodified to Klarna’s Payment Authorization API.
• Validation can and should be implemented, but it must not be more restrictive than what is specified in Klarna’s Payment Authorize APIAPI. Make sure that all special characters permitted by the API specification are accepted.

Sample request

Below an example of how Acquiring Partners can accept the interoperability parameters in their Payment request API endpoint.

{
  "currency": "USD",
  "amount": 17800,
  "payment_method_options": {
    "klarna": {
      "interoperability_token": "eyJhbGciOiJ...",
      "interoperability_data": "{\"content_type\":\"application/vnd.klarna.interoperability-data.v2+json\",\"content\":{\"payment_request\":{...}}}"
    }
  }
}

Supplementary purchase data

Supplementary purchase data improves Klarna’s ability to assess risk, optimize approval rates, and deliver a more personalized checkout experience. It includes structured information such as line items, L2/L3 data for Card Network optimization and other transaction context.
Acquiring Partners may receive this data from the Partner in two ways:

1. Embedded in interoperability_data
   1. No parsing needed. Just forward it as-is.
2. As individual fields in the Acquiring Partner’s API
   1. The Acquiring Partner is responsible for mapping existing fields in their payment API with the fields defined in the supplementary_purchase_dataAPI object when calling the Payment Authorize APIAPI.

​

Read more about Supplementary Purchase Data here.

Sample Subscription request with existing token

curl -X POST "https://api-global.klarna.com/v2/payment/authorize" \
  -H 'Authorization: Basic <API key>' \
  -H 'Content-Type: application/json' \
  -H 'Klarna-Interoperability-Token: eyJhbGciOiJIU...' \
  -H 'Klarna-Customer-Token: krn:customer-token:123' \
  -d '{
    "currency": "USD",
    "supplementary_purchase_data": {
      "subscriptions": [{
        "subscription_reference": "MONTHLY PLAN",

For a customer not present token charge the Payment Authorize API can yield 2 different outcomes depending on the transaction and the consumer:

Approved Payment Transaction

When the request is successful, a Payment Transaction is created on Klarna Network and will be available for post-purchase operations through the Payment Transactions API. No further customer interactions are needed and the Acquiring Partner can directly inform their partners that the payment session is completed and that the customer can be redirected to the order confirmation page.

Acquiring Partners must store the Klarna payment_transaction_id for future operations on the transaction through the Payment Transactions API, such as capture and refund. The Acquiring Partner will receive the following parameters in the response.

Response body

The response will contain a payment_transaction_responseAPI object with the following parameters:

Sample response - APPROVED

{
  "payment_transaction_response": {
    "result": "APPROVED",
    "payment_transaction": {
      "payment_transaction_id": "krn:payment:eu1:transaction:6debe89e-98c0-[...]",
      "payment_transaction_reference": "acquiring-partner-transaction-reference-1234",
      "amount": 11800,
      "currency": "USD",
      "payment_funding": {...},
      "payment_pricing": {...}

Declined authorization

If a transaction could not be approved by Klarna and step-up scenario cannot be triggered (due to missing configuration or for permanent decline), the Acquiring Partner will receive a decline. Declines should not be replayed without change of context.
The Acquiring Partner should inform the Partner that the payment could not be completed and the Partner should invite the customer to select another payment method.

Response body

The response will contain a payment_transaction_responseAPI object with the following parameters:

Sample response - DECLINED

{
  "payment_transaction_response": {
    "result": "DECLINED"
  }
}