Buy now, pay later sounds like a dream: split your purchase into four easy payments, zero interest, no credit check. It’s no wonder US Pay-in-4 BNPL volume hit $70 billion in 2025 (Federal Reserve Bank of Richmond, February 2026). Affirm, Klarna, and Afterpay are now embedded in checkout flows at thousands of retailers, from Amazon to your local boutique.

But here’s the question nobody asks at checkout: if it’s free for you, how are these companies making billions of dollars?

The answer is more complicated, and more consequential for your finances, than the marketing suggests. This is the buy now pay later trap, and understanding it is the first step to avoiding it.

The ‘Free Loan’ Illusion

BNPL companies have mastered the art of the zero-interest pitch. "Pay in 4. No interest. No fees: if you pay on time." That last clause is doing a lot of heavy lifting.

The 0% interest offer is real, for the consumer, under ideal conditions. But BNPL platforms are not charities. They are venture-backed (and in Klarna's case, publicly traded) businesses with investors expecting returns. The money has to come from somewhere.

What BNPL has built is a multi-layered revenue model that monetizes merchants, monetizes consumer mistakes, and increasingly monetizes consumer attention. The “free loan” is the hook. The business model is everything that happens around it.

How BNPL Companies Really Make Their Money

BNPL revenue streams are more diverse than most users realize. Here’s a breakdown of each one.

Merchant Fees: The Hidden Tax on Every Purchase

When you use Klarna or Afterpay at checkout, the retailer pays a fee, and it's steep. BNPL platforms charge merchants 2–8% per transaction, compared to roughly 2% for traditional credit cards. That premium exists because BNPL drives higher conversion rates and larger basket sizes, and merchants pay for that lift.

The numbers are specific:

  • Klarna’s average merchant fee on a $100 transaction: $2.69
  • Sezzle charges 6.1% + $0.30 per transaction
  • Merchant fees represent 32–57% of total BNPL revenue (Congressional Research Service, February 2026)

In other words, every time you split a purchase, the retailer is quietly subsidizing your "free" loan, and passing some of that cost back to all consumers through pricing.

Late Fees: Profiting From Forgetfulness

BNPL companies insist they don’t want you to pay late. That may be true. But late fees are still a meaningful revenue line.

  • The average late fee assessed in 2023 was $9.99 (CFPB, December 2025)
  • 4.1% of Pay-in-4 loans were assessed late fees
  • Klarna made 17% of its revenue from consumer fees in 2024
  • Sezzle made 22% of its revenue from consumer fees in 2024

At scale, even a small percentage of late payers adds up to hundreds of millions of dollars annually. The business model doesn't require most users to pay late: just enough of them.

Interest on Longer-Term Installment Loans

Pay-in-4 gets the headlines, but BNPL companies also offer longer-term financing, and that's where interest charges enter the picture.

Affirm’s longer-term loans can carry APRs up to 36% (higher than many credit cards). And this isn't a niche product: interest income accounts for 52% of Affirm’s total revenue. The “buy now pay later” brand is built on the interest-free promise, but the majority of Affirm’s money comes from interest-bearing loans.

If you’ve ever clicked through to a 12- or 24-month payment plan at checkout, you may have signed up for a loan that costs more than a credit card would have.

Advertising Revenue: Your Attention Is the Product

Klarna, Afterpay, and Affirm have all built shopping apps and discovery platforms. Merchants pay to have their products featured, sponsored, or promoted within these apps.

This turns BNPL platforms into media companies. Your browsing behavior, purchase history, and financial profile make you a highly targeted advertising audience. The checkout tool becomes a shopping channel, and the shopping channel sells your attention back to retailers.

Subscriptions: Paying for the Privilege

Some BNPL platforms have introduced subscription tiers that unlock perks like higher spending limits, fee waivers, or exclusive offers.

Sezzle generates approximately 30% of its revenue from subscriptions. This model shifts BNPL from a transaction-based business toward a recurring revenue model, and it means some users are paying monthly just to access the service.

BNPL Banks on You Forgetting

The most elegant part of the BNPL business model is how it exploits the limits of human memory and attention.

When you split a $200 purchase into four $50 payments, the first payment feels trivial. The second payment is two weeks away: easy to forget. By the time the third and fourth payments hit, you may have made three or four other BNPL purchases, each with their own staggered schedules.

The data confirms this is a widespread problem:

  • 47% of BNPL users paid late at least once in the past year (LendingTree 2026 Report), up sharply from 34% in 2024
  • 68% of BNPL users say the service causes them to overspend
  • Most BNPL plans are tied to autopay on a checking account, meaning a missed payment can trigger an overdraft fee on top of the BNPL late fee

This isn't a design flaw. Staggered, easy-to-forget payment schedules are a feature of the product, one that benefits the platform when users slip up.

The Loan Stacking Problem

One BNPL plan is manageable. Three or four running simultaneously is where things get dangerous, and it's more common than you'd think.

62% of BNPL borrowers took out simultaneous transactions across different providers (CFPB). The average BNPL borrower took out 6.3 Pay-in-4 loans in 2023 alone. That's potentially dozens of individual payment dates spread across Affirm, Klarna, Afterpay, and others, with no single place to see them all.

Research from Harvard Business School found that BNPL users had a higher likelihood of overdraft and lower checking account balances compared to non-users. The mechanism is straightforward: autopay withdrawals from multiple BNPL providers, hitting a checking account on unpredictable dates, drain balances faster than users anticipate.

This is the buy now pay later trap in its most concrete form: not one bad decision, but the accumulation of many small, seemingly harmless ones, until the checking account runs dry.

How a BNPL Tracker Tool Keeps You in Control

Knowing how the system works is half the battle. The other half is having the right tools to stay on top of it.

My Debt Coach’s BNPL tracker is built specifically for this problem. Instead of juggling payment dates across multiple apps and email confirmations, you get:

  • All your BNPL payment dates in one place: Affirm, Klarna, Afterpay, Sezzle, and more
  • Reminders before due dates, so you're never caught off guard by an autopay withdrawal
  • A real-time view of your total BNPL debt, because knowing what you owe is the first step to managing it
  • Late fee avoidance: the tracker's whole purpose is to make sure you never pay $9.99 for forgetting a due date

This isn't about guilt or restriction. It's about having the same information the BNPL companies have, and using it to your advantage instead of theirs.

Sources

  • LendingTree 2026 BNPL Report
  • CFPB December 2025 BNPL Market Report
  • Congressional Research Service, February 2026
  • Federal Reserve Bank of Richmond, February 2026
  • Harvard Business School research on BNPL and consumer financial health

Take Control of Your BNPL Payments

Take control of your BNPL payments before they take control of you. My Debt Coach's free BNPL tracker gives you a single dashboard for every payment plan you're running, so you always know what's due, what's coming, and what it's costing you. Start tracking for free today at mydebtcoach.com.