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A 2026 buyer's guide to Affirm, Klarna, Afterpay, Shop Pay Installments and Sezzle, organized around the merchandise categories where each provider actually earns its fee. Pricing and terms verified September 10, 2026.

What follows is the same session we walk a founder through when a new payment button shows up in a board deck as a growth lever, done with every provider's own pricing page pulled fresh this morning rather than a chart somebody wrote eighteen months ago. It runs about seven minutes, and by the end you will know which of these five providers actually indexes well for the category you sell in, what the obligation to a lending partner really costs once volume clears roughly a thousand orders a month, and the two questions worth asking a sales representative before signing anything with a term longer than a season.

What this guide covers

• Why the honest question is not which provider is best overall, but which one converts your specific shopper without discounting a sale that was already coming.

• The arithmetic that actually matters: a merchant fee measured against incremental order value, not against total installment volume.

• Affirm, Klarna, Afterpay, Shop Pay Installments and Sezzle, with every publicly verifiable term, structure and named vertical, and an honest note on what none of the five will publish.

• A side-by-side table, then a recommendation sorted by category rather than by brand size.

• The questions founders ask us before they sign an installment agreement, including whether it cannibalizes full-price sales and what happens to a return mid-cycle.

The short version. None of these five providers publishes a merchant discount rate, so no comparison table in this category can respond to your actual invoice, and every number quoted to your business will be negotiated privately against your volume and average order value. What can be verified is which category each provider is built around. Affirm is the only one of the five that names Auto as a standalone industry on its own business site, alongside Home & lifestyle, Fashion, Fitness & sporting goods and Travel, lining up with the higher ticket sizes its longer terms are built to carry. Afterpay's own storefront foregrounds Health & Beauty and Fashion ahead of everything else, consistent with the younger, frequent-purchase audience it has always marketed toward. Shop Pay Installments is underwritten by Affirm behind the scenes, so a Shopify-native brand selling apparel or home goods inherits Affirm's approval logic without a second lending relationship to manage. Klarna's own storefront directory spans Automotive, Electronics, Fashion, Health & Beauty and Garden & Patio broadly enough that no single vertical claim holds up, making it a reasonable default rather than a specialist. Sezzle markets itself around building credit and financial access, a positioning that suits general merchandise more than considered, higher-AOV purchases. None of that changes the arithmetic underneath the decision: the merchant fee against the orders it actually creates, not against every order that runs through the button regardless.

The question worth asking before any of this

The volume threshold that matters here sits around a thousand orders a month, roughly where every provider's underwriting terms begin to shift in a merchant's favor, and it is directional rather than a hard gate: a brand doing four hundred orders at an average order value of three hundred fifty dollars moves more dollar volume than one doing fifteen hundred orders at sixty dollars each, and lending partners increasingly underwrite against revenue and repayment behavior rather than order count alone, so a low-volume, high-AOV brand should not assume the door is closed. The second qualifying question is whether your category's return rate is high enough that a mid-cycle return creates a reconciliation headache, since providers differ in how quickly they refund a canceled obligation, a difference that matters more in apparel and footwear than elsewhere. The third is whether your checkout already carries a loyalty mechanic, since stacking an installment option on top of a points program without testing the combination can quietly suppress full-price purchases in the exact segment you are trying to protect.

What independent data actually shows

The Consumer Financial Protection Bureau's most recent market spotlight, published in December 2025 from aggregate data spanning six large providers across 2019 through 2023, found that the number of consumers taking out at least one buy now, pay later loan reached 53.6 million in 2023, a twelve percent increase over the prior year, with the average dollar amount borrowed from a single lender rising to eight hundred forty eight dollars after inflation. The same report found late fee incidence falling rather than rising, 4.1 percent of loans assessed a fee in 2023 against 5.2 percent in 2022, and charge-offs dropping to 1.83 percent from 2.63 percent, suggesting credit quality among this borrower base is improving even as usage grows. None of that breaks out by merchandise category or discloses what any provider charges a merchant, which is exactly why a brand cannot borrow someone else's blended rate and expect it to apply to its own invoice.

What actually separates these five providers

Underwriting relationships matter more than the checkout button suggests. Shop Pay Installments is not an independent lender; it runs on Affirm's underwriting behind a Shopify-native interface, so a merchant running both is exposing the same shopper to the same credit decision twice, not diversifying approval odds.

Term length is the real differentiator, not the interest-free pitch. All five offer some version of a four-payment, interest-free split, but only Affirm, Klarna and Shop Pay Installments publicly describe longer monthly terms up to roughly thirty six percent APR, which matters for anything selling above a few hundred dollars a unit.

Category self-selection shows up in each provider's own marketing, not in any performance data they release. Afterpay and Sezzle both market toward a younger, lower-AOV shopper, while Affirm leans toward considered, higher-ticket categories including auto parts and furniture, a positioning signal rather than a guaranteed approval outcome.

None of the five will tell a founder what the fee actually is until a contract is on the table. That is the largest gap between how this category is written about and how it gets purchased, and why a merchant should request a live quote rather than repeat a percentage from a blog post that may be years stale.

Affirm

Source: affirm.com/business, read live September 10, 2026. Rates and terms vary by merchant and by shopper creditworthiness; Affirm states example terms rather than a single published rate.

Affirm is the only one of the five that names Auto as a distinct industry on its own business marketing, alongside Home & lifestyle, Fashion, Fitness & sporting goods and Travel, signaling the merchant categories its underwriting model was built around. Its consumer product splits into two tiers: an interest-free four-payment option for smaller purchases, and a longer monthly installment loan running from three months out to two years or more, with published APR ranging from zero to thirty six percent based on credit. For a brand selling aftermarket auto parts, tires, outdoor power equipment or furniture, where average order value regularly clears several hundred dollars, Affirm's positioning suggests it is built around that conversation, though no public data confirms a higher approval rate in that category specifically. Affirm publishes no merchant discount rate anywhere on its site, so the fee has to be requested directly and will move with volume and average order value.

Klarna

Source: klarna.com/us/business, read live September 10, 2026. Example given on the live page: a $1,000 purchase over six months runs roughly $173.53 a month at 13.99% APR, with rates ranging from 0.00% to 35.99% depending on the shopper's credit.

Klarna's own shopping directory spans Automotive, Electronics, Fashion, Health & Beauty, Garden & Patio and more, broadly enough that no single vertical claim holds up the way Affirm's Auto positioning does, making it a reasonable default for a brand that does not fit neatly into one of the other four providers' lanes. Its financing product runs the longest published term range of the five, up to thirty six months on select purchases, suiting durable goods where a shopper genuinely wants to spread a large purchase across more than a year. The pay-in-four option mirrors the rest of the category, four interest-free biweekly payments with no published merchant rate, and Klarna's own disclosures are unusually specific about example payment amounts, giving a founder something concrete to model before requesting a real quote.

Afterpay

Source: afterpay.com/en-US, read live September 10, 2026. The site's own language: "Choose to pay over 3, 6, 12 or 24 months or in 4 interest-free payments at partner brands."

Afterpay's own shopper-facing directory leads with Health & Beauty and Fashion ahead of Home & Garden and Electronics, an ordering that reflects the category mix the brand has cultivated since launch and historically skews toward a younger shopper making frequent, lower-ticket purchases. That profile suits a beauty or fashion brand whose average order sits well under two hundred dollars, whose customer already associates the Afterpay name with the category from other stores she shops, a brand-recognition advantage none of the other four fully replicate. The monthly option extending to twenty four months exists only at participating brands, and Afterpay does not disclose its own consumer APR for that tier, worth confirming directly before assuming parity with Affirm's or Klarna's published ranges.

Shop Pay Installments

Source: shopify.com/shop-pay-installments, read live September 10, 2026. Shopify's own claim on the page: businesses offering installments can increase average order value by up to 50%, an internal figure attributed to Shopify rather than an independent audit.

Shop Pay Installments is the one product here a founder does not shop for independently. Built into Shopify checkout and underwritten entirely by Affirm's lending relationships, a Shopify-native brand already running Affirm elsewhere is not adding a second lender so much as surfacing the same one under a different name. Its structure splits into a Standard tier covering fifty to a thousand dollar purchases with two or four interest-free payments plus monthly options up to twelve months, and a Premium tier extending from thirty five dollars up to thirty thousand dollars with longer terms, giving a merchant selling both everyday and considered purchases one integration rather than two. The appeal is the native checkout and no second app to reconcile; the tradeoff is that a brand cannot meaningfully test it against Affirm as a separate decision, since in practice they share the same underwriting.

Sezzle

Source: sezzle.com/business, read live September 10, 2026. Sezzle's own site markets on-time payment reporting as a credit-building feature rather than emphasizing longer monthly financing terms.

Sezzle is the outlier of the five in how directly it markets to the shopper rather than the merchant, positioning itself around financial access and on-time payment reporting that helps a shopper build credit history, a framing none of the other four lead with as clearly. That resonates with a budget-conscious shopper making frequent, general-merchandise purchases rather than financing a single large-ticket item, a reasonable fit for value-priced apparel and everyday categories where the four-payment split does the whole job. Sezzle's own site does not publish a monthly option past the standard four-payment structure the way Affirm, Klarna and Shop Pay Installments do, so confirm directly whether a longer term exists at all before assuming it does.

Side by side

All figures verified live September 10, 2026 directly from each provider's own business or consumer-facing page. No provider publishes a merchant discount rate; any percentage quoted elsewhere should be treated as unverifiable until confirmed in a live merchant agreement.

The recommendation, by category

A beauty or fashion brand with an average order under two hundred dollars, whose shopper already recognizes Afterpay from other stores, gets the most brand-recognition value from its four-payment product, though nothing here proves a higher approval rate over Klarna or Sezzle for that same shopper. A brand selling aftermarket auto parts, outdoor equipment or furniture with an average order comfortably above three hundred dollars is better served starting with Affirm, the only provider naming Auto as a standalone vertical and the only one whose longer terms are built around considered purchases from the outset. A Shopify-native brand that wants one integration rather than two should default to Shop Pay Installments, which removes an app and a reconciliation process without changing the lending relationship underneath it. A home goods or general merchandise brand without a strong category lean is reasonably served by Klarna, whose storefront spans enough categories to function as a credible default. A value-priced or younger-skewing brand where the four-payment split alone does the conversion work is the clearest fit for Sezzle. In every case, the fee that determines whether the math works is not published anywhere on these five companies' own sites, and it should be requested in writing, against your real order volume, before a contract is signed.

Questions we get asked

Does buy now, pay later actually increase average order value on Shopify?

Shopify's own marketing for Shop Pay Installments claims an increase in average order value of up to fifty percent, a figure attributed to Shopify rather than an independent study, and it should be read as a ceiling under ideal conditions rather than a typical result across every catalog.

Which provider is the lowest paid price for a small brand under a thousand orders a month?

None of the five publishes a rate card a small brand can compare without a live quote, so the honest answer is that the least expensive route is the one negotiated against your specific volume, not any percentage repeated in a comparison article.

Do these providers cannibalize full-price sales that would have happened anyway?

Some portion of every installment transaction is incremental and some would have converted regardless, and the CFPB's own data on rising loan sizes per consumer suggests usage is broadening rather than staying confined to marginal purchases, which argues for testing the fee against a controlled cohort rather than assuming either extreme.

Can a brand offer more than one of these providers at checkout?

Yes, and many mid-market Shopify merchants run two or three side by side to match shopper preference, though running Shop Pay Installments alongside Affirm specifically duplicates rather than diversifies underwriting, since both route through the same lending relationship.

What happens to the installment obligation if a shopper returns the item?

Each provider handles a return differently in how quickly remaining installments are cancelled and the paid portion refunded, and that detail lives in each provider's merchant agreement rather than its public marketing page, so confirm it before launch in any category with an above-average return rate.

Does a brand under a thousand orders a month even qualify for these programs?

Order count is a directional signal rather than a hard requirement, since a lower-volume brand with a high average order value can often qualify for the same terms as a higher-volume, lower-AOV brand, because most providers underwrite against total dollar volume and repayment behavior rather than order count alone.

Where to go next

If your team is weighing an installment button against the arithmetic of a real customer file rather than a marketing claim, that is the kind of modeling we do inside conversion rate optimization and checkout build work for clients ranging from aftermarket vehicle parts to considered fashion. We have run this exact test for UTV Source, whose customer buys higher-ticket aftermarket parts on a purchase cycle installment financing is built for, and for Moonglow Jewelry, where a considered purchase at a different price point needed a different answer entirely. If you would rather pair an installment decision with the lifecycle messaging that reminds a shopper her next payment is due, or connect the data to a Klaviyo flow rather than letting it sit in a separate dashboard, get in touch and we will walk through your actual order file rather than a generic one.