# Buy Now, Pay Later at Checkout: The Fee Math Before the Lift

Source: https://checkoutconversionlab.com/blog/2026-11-10-buy-now-pay-later-checkout-fee-math.html

A shopper with a 180 dollar basket hovers over the pay button. Four payments of 45 dollars feels different from one charge of 180 dollars, and that feeling is the whole product. The question for the store is not whether shoppers like it. It is whether the fee on every BNPL order is smaller than the revenue the option adds, and most stores answer that question by reading the provider's marketing page instead of doing the arithmetic.

## What the provider actually charges

The fee is the part nobody puts on the landing page. Klarna charges merchants around 3.29 percent plus 30 cents per transaction in the US. Afterpay runs about 4 to 6 percent plus 30 cents. Affirm charges 2 to 8 percent depending on the financing term, with longer terms costing more. Standard card processing sits near 2.9 percent plus 30 cents, so BNPL costs roughly 1.5 to 3 extra percentage points on every order that uses it. On a 120 dollar order at 4.5 percent plus 30 cents, that is 5.70 dollars against about 3.78 dollars on a card. The provider pays you the full purchase price upfront, minus that fee, and takes the repayment risk. If the shopper falls behind, the provider eats it, and the late fee goes to the provider, not to you. That risk transfer is the only thing the premium buys. Everything else about the fee is cost.

The standard product is pay in four: 25 percent at checkout, then three equal installments every two weeks, interest free if paid on time. Roughly 96 million people in the US are expected to use BNPL in 2026, and about 16 percent of US adults used a BNPL service in the past year, up from 10 percent in 2021. The shoppers are there. The question is whether they are your shoppers, and whether the ones who use it were going to buy anyway.

## The lift numbers, and who reported them

Provider studies report conversion lifts of roughly 20 to 30 percent and average order value lifts of 30 to 85 percent. Affirm told the SEC its merchants reported 85 and 92 percent higher average order values in internal studies from 2019 and 2018. Klarna claims merchants see about a 45 percent increase in average order value. Afterpay reports a 22 percent increase in conversion rate. Every one of those numbers is self reported by a company with an obvious interest in promoting its product, measured on merchants who chose to install it, with no clean control group. The honest reading is narrower: BNPL widens who can afford the product. It does not decide whether someone wants it. On a 34 dollar impulse buy, adding Klarna moves almost nothing. On a 1,400 dollar mattress, it moves a lot, because the installment turns a considered purchase into a monthly line item. The lift concentrates in furniture, fashion, and electronics, exactly the verticals the providers quote.

Regulation is still moving under it. The CFPB issued an interpretive rule in 2024 treating BNPL lenders as credit card issuers under Regulation Z, then withdrew it in May 2025 and said it did not plan to reissue a revised version. In the EU, the revised Consumer Credit Directive brings BNPL under consumer credit rules, with member states to implement by November 2026. None of that changes the fee math today, but it means the compliance cost of offering BNPL is not zero and not settled.

## The test that settles it for your store

Offer it only above a threshold, say orders over 100 dollars, and measure three things against a control group: completion rate, average order value, and gross margin per completed order. If the order value lift is the same shoppers splitting the same basket, the fee is pure cost. If completion rises and the new orders carry your normal margin, the fee is buying real revenue. Run it for at least four weeks, because BNPL usage spikes around paydays and drops between them, and a one week test will lie to you in either direction. And put the BNPL price on the product page, not only at checkout. A shopper who discovers the installment option at the payment step has already decided; the option only changes the decision when it is visible before the cart. If the math does not clear after a month, turn it off. The providers will call that a mistake. The fee schedule says otherwise.

Keep reading: [Express Checkout: Setup Guide for Faster Buying](2026-11-03-express-checkout-guide.md), [Wallet buttons above or below the form: the order is a segmentation question](2026-11-04-checkout-wallet-buttons-above-or-below-form.md), [Payment Errors at Checkout: Recovery, Not Rejection](2026-11-08-checkout-payment-error-recovery.md).

## Frequently asked questions

### How much does buy now, pay later cost a merchant per order?

Klarna charges roughly 3.29 percent plus 30 cents in the US, Afterpay roughly 4 to 6 percent plus 30 cents, and Affirm 2 to 8 percent depending on the financing term. Standard card processing runs near 2.9 percent plus 30 cents. On a 120 dollar order at 4.5 percent plus 30 cents, BNPL costs 5.70 dollars against about 3.78 dollars on a card.

### Does BNPL actually lift conversion, or is that provider marketing?

Provider studies report conversion lifts of roughly 20 to 30 percent and average order value lifts of 30 to 85 percent, but those come from merchant self-reports with no clean control group and lean toward higher ticket carts. Affirm told the SEC its merchants reported 85 and 92 percent higher average order values in internal studies. Treat the lift as real for expensive baskets and unproven for cheap ones.

### What is the standard pay-in-4 schedule?

The shopper pays 25 percent at checkout and the remaining 75 percent in three equal installments every two weeks, with no interest charged if payments are made on time. Late fees typically run 7 to 15 dollars per missed payment. Longer term financing from the same providers can carry interest up to 36 percent APR.

### Should a low ticket store offer BNPL?

Probably not. The fee premium of 1.5 to 3 percentage points is only justified when the conversion lift or the order value increase more than compensates. A store with 60 percent gross margins and orders over 100 dollars can test it profitably. A store with 20 percent margins selling 30 dollar items usually pays the fee and gets no measurable lift.