Coming soon (Q3 2021), Klarna as an alternative payment method will be available using Shopify's new Payments Platform. (As of December 31, 2021, existing HPSDK integrations, including the current Klarna Payments HPSDK integration, will be deprecated by Shopify, and will no longer be able to process payments, per: https://shopify.dev/docs/hosted-payment-sdk)
By default, shipping phone number is optional in Shopify checkout, but Klarna Payments requires that both phone and email are supplied. If the phone number or email is not provided to Klarna, on redirect from Shopify, the consumer will be given an error message and redirected back to the Shopify checkout. To avoid errors and provide a streamlined consumer experience, set phone number as required in Shopify admin by navigating to Settings → Checkout → Form options:
To require email in Shopify Checkout, under Shopify admin → Settings → Checkout → Customer contact, choose the “Customers can only check out using email”.
The locale for Klarna Payments locale will be set based on the store's locale concatenated with the customer's billing address country and are not currently configurable, e.g. English language selected for a customer with a US billing address entered in Shopify checkout would result in a request locale of 'en-US' when Klarna Payments is loaded. If the requested locale is supported by Klarna Payments, per: Available purchase countries, currencies and locales, the locale will be honored. If the locale is not supported, English is used as a fallback.
When the order is placed in Shopify, a payment id is set in the Shopify order Timeline information under the "payment was processed on Klarna." section, within the "Information from the gateway" subsection. This payment id is set in the Klarna order's merchant reference 1 and 2. (Shopify does not share the Shopify order id for this payments app integration for Klarna to be able to associate the Shopify order id or order name in the Klarna order.)
Initially, only the production Klarna account (and merchant portal) will be supported for test orders for this payments integration; a production merchant account (MID) will be required to place test mode orders with the Klarna payment method in a Shopify store. (Klarna's playground Klarna merchant portal is used or supported for the payment method app).
Klarna does NOT pay out for test mode orders. Make sure to uncheck Test Mode in the alternative payment method in your Shopify admin configuration for live stores!
Note: test orders will not be visible in the Klarna merchant portal (but test orders will show in the Shopify store admin if the order was completed); production orders will be visible in both the Klarna production merchant portal and the Shopify store admin.