Buy Now Pay Later: How Installment Services Work for Merchants

The short answer

Buy Now Pay Later (BNPL) is a payment method where the customer splits a purchase into several payments, often without interest for the customer. For the merchant it looks like a regular payment method at checkout:

1. The customer chooses "Pay in installments" at checkout.
2. The BNPL provider checks the customer and approves a limit, usually within seconds.
3. The customer pays the first part or nothing upfront, depending on the plan.
4. The provider pays the merchant the full order amount minus its fee.
5. The customer repays the provider according to the schedule.

The key point: in the classic model the provider, not the merchant, carries the credit risk. If the customer does not repay, it is the provider's problem.

Models: who bears the risk

In-house installments look cheaper at first, but the merchant becomes a lender: it needs scoring, reminders, debt collection and enough working capital. For most stores a provider is simpler.

Rules for consumer credit and installment products differ by country, including requirements for licensing, disclosure of terms and, in some markets, Sharia-compliant structures. Check what applies in yours.

Merchant fees: what they depend on

BNPL is usually more expensive for the merchant than card acquiring, because the fee covers the provider's credit risk and the customer's interest-free period. The fee depends on:

• installment term — longer plans usually cost the merchant more;
• product category and average check;
• volume you bring to the provider;
• who pays interest — merchant, customer or shared;
• refund and chargeback terms.

Compare offers by the full cost per successful order, including refunds and payout timing, not only by the headline percentage.

Checkout integration

A typical integration has these parts:

• Payment method at checkout — a redirect to the provider page, a widget or an SDK in the mobile app.
• Order creation API — you send items, amount, customer contacts and return URLs.
• Webhooks — notifications about approval, rejection, cancellation and completed payment. Confirm the order only after a verified webhook, not after the customer returns to the success page.
• Refunds and partial refunds — via API, so that returns in the store adjust the customer's schedule.
• Price messaging — showing "from X per month" on product and cart pages, calculated with the provider's rules.
• Reconciliation — matching provider payouts with orders in your accounting or ERP system.

For marketplaces and stores with offline points, the provider may also offer QR codes or a merchant app for in-store sales.

Effect on conversion and average check

Merchants add BNPL mainly for two reasons:

• Conversion. Some customers abandon expensive carts because of the one-time amount. Splitting it lowers the barrier.
• Average check. When the monthly payment looks manageable, customers may choose a more expensive model or add accessories.

The real effect varies by category, price level and audience. Measure it yourself: compare conversion and average order value for orders with and without BNPL, and watch the share of returns and cancellations.

Common mistakes

• Showing the installment option only on the last checkout step, when the decision is already made.
• Confirming orders without waiting for the provider's final status.
• Not syncing returns, so customers keep paying for returned goods.
• Ignoring how fees change with longer terms and promotional plans.
• Hiding the terms: customers should clearly see the schedule and any costs.