Klarna lets shoppers spread or delay payment while the retailer is paid in full. It was founded in Stockholm in 2005 and listed on the New York Stock Exchange in September 2025. In the second quarter of 2026 it reported 120 million active consumers, more than 1.2 million merchants and $36.6 billion of sales.
UK shoppers can pay in full, pay in 3, pay in 30 days or take longer financing. Klarna’s UK business is authorised and regulated by the Financial Conduct Authority.
Paid upfront
Retailers are paid upfront and in full whichever option the shopper picks, and Klarna takes on the credit and fraud risk. Express checkout, on-site messaging and Sign in with Klarna sit alongside the payment options.
Since 15 July 2026, the FCA has regulated buy now, pay later in the UK, bringing affordability checks, access to the Financial Ombudsman and Section 75 protection.
Ways to offer it
Most retailers add Klarna through their payment provider. Its partners include Stripe, Adyen, Worldpay, Checkout.com and Mollie, and on Shopify it’s available through the main payment plugins, Shopify Payments included. WooCommerce and Adobe Commerce have their own integrations.
Klarna is also preparing for AI shopping. It backed Google’s agent payments protocol in October 2025, launched an Agentic Product Protocol in December, and added a ChatGPT shopping app in May 2026.
The APIs
A direct integration uses the Klarna Payments API, or a hosted payment page Klarna runs. After the sale, the Order Management API captures, refunds, cancels and extends orders.
The Settlements API returns payouts and the transactions inside them, with CSV and PDF reports also available in the Merchant Portal or by SFTP. Requests authenticate with an API key, and a playground environment handles test purchases without touching live systems. Production allows up to 200 requests a second for most operations.
Same basket, different fee
Klarna appears by name in our order-level P&L case study: a Klarna sale and a Shopify Payments sale for the same amount end up with different profit figures, because each provider’s contract charges differently. The engine reads which method the customer used on every order and applies the right fee.
Matching settlements to orders is the other half of the job. Pricing the manual version is the first step, and five warning signs show when it’s already costing money.