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Personal Finance · head to head

Affirm vs Basis Theory

Affirm logo

Affirm

Personal Finance

Buy now pay later app offering short interest-free plans and longer plans that charge real APR interest

From
Free
Rated
-
Full reviewWebsite
Basis Theory logo

Basis Theory

APIs

Developer tokenisation platform that holds card and sensitive data inside a PCI Level 1 environment you do not operate

From
$995/month
Rated
-
Full reviewWebsite

The short version

  • Only Affirm has a free tier, so it costs nothing to try first.
  • Each has a real cost: Affirm longer instalment plans carry real interest, up to roughly 36 percent APR depending on the retailer, item and applicant, which is a genuine borrowing cost that the buy now pay later framing can obscure for shoppers who do not read the terms shown before accepting.; Basis Theory the Starter plan is 995 US dollars a month before any volume, which is a real floor for an early stage company and puts the product out of reach of teams tokenising a few thousand records.
  • They diverge on capability: Affirm covers Pay in 4, Basis Theory covers Tokenisation API.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Affirm and Basis Theory actually diverge.

Attributes where Affirm and Basis Theory differ
AttributeAffirmBasis Theory
Starting priceFree$995/month
Pricing modelFree for short Pay in 4 plans; longer plans carry a disclosed APR up to roughly 36 percent, merchant pays a transaction feePer month by token volume
Free tierYesNo
PlatformsiOS, Android, WebWeb, iOS, Android, Linux
CategoryPersonal FinanceAPIs

Identical on both: user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Affirm

  • Pay in 4
  • Monthly instalment loans
  • Soft credit check
  • No late fees
  • Affirm Card
  • Pre-purchase terms disclosure

Only in Basis Theory

  • Tokenisation API
  • Hosted elements
  • Outbound proxy
  • PCI attestation of compliance
  • Processor portability
  • Reactors
  • Access controls and audit
  • PII and PHI options

What people use each for

The jobs each tool is most often brought in to do.

Affirm

  • A shopper financing a large purchase such as furniture or electronics who wants disclosed APR terms compared directly against a credit card before committingnot Basis Theory
  • Someone using the short Pay in 4 plan for a smaller purchase who intends to pay it off within six weeks with no interestnot Basis Theory
  • A borrower who has missed a payment before and specifically wants a lender that does not charge late feesnot Basis Theory
  • A retailer offering point-of-sale financing to reduce cart abandonment on higher-ticket items, in exchange for paying Affirm a transaction feenot Basis Theory

Basis Theory

  • A payments company that wants card on file without bringing its own infrastructure into PCI scope and paying for the assessment that followsnot Affirm
  • A merchant locked into a processor by that processor vault that wants to hold its own tokens and route to more than one acquirernot Affirm
  • A fintech collecting bank account and identity data that needs it isolated from its application database before an enterprise security reviewnot Affirm
  • A team that needs to send stored card data to a third party for a one-off integration without that data traversing its own serversnot Affirm

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Affirm

  • Longer instalment plans carry real interest, up to roughly 36 percent APR depending on the retailer, item and applicant, which is a genuine borrowing cost that the buy now pay later framing can obscure for shoppers who do not read the terms shown before accepting.
  • Even with no late fees, Affirm reports many loans to credit bureaus, so a missed or late payment on a longer plan can affect a credit score in a way the marketing around interest-free short plans does not prepare shoppers for.
  • Approval and APR both vary by individual loan, so the same shopper can be offered interest-free terms on one purchase and a high APR on another, making the cost unpredictable until checkout.
  • Merchants pay a transaction fee to offer Affirm at checkout, a cost typically built into retail pricing, so shoppers who pay by other means still indirectly subsidise the option even if they never use it.
  • The Affirm Card blurs the line between buy now pay later and a general-purpose credit card, and using it for everyday spending on interest-bearing terms can compound borrowing cost in a way a single point-of-sale purchase would not.

Basis Theory

  • The Starter plan is 995 US dollars a month before any volume, which is a real floor for an early stage company and puts the product out of reach of teams tokenising a few thousand records.
  • Starter is limited to the US region, so a company with European data residency requirements is pushed into a quoted Scale or Enterprise agreement immediately.
  • Log retention on Starter is 24 hours, which is well below what most security teams expect for a system holding cardholder data and forces an upgrade for reasons unrelated to volume.
  • Migrating away means moving card data out of the vault, which requires processor and assessor involvement and is slow, so the portability argument that attracts buyers cuts against them at exit.
  • An attestation of compliance covers the vendor environment, not your assessment; your assessor still decides what is in scope, and buyers occasionally discover their integration pattern pulled systems back into scope anyway.

Pricing, plan by plan

Affirm

Free
  • Pay in 4Free
    • No interest if paid on time over six weeks
    • No late fees for a missed payment
    • Soft credit check at application
  • Monthly instalmentsFree
    • APR disclosed before the loan is accepted, up to roughly 36 percent depending on retailer and applicant
    • Terms from three to 36 months depending on purchase amount
    • Payment history can be reported to credit bureaus

Basis Theory

$995/month
  • Starter$995/month
    • 20,000 tokens included
    • Production PCI Level 1 environment
    • US region only
  • Scale$undefined/month
    • Quoted
    • Higher token volumes
    • Additional regions
  • Enterprise$undefined/month
    • Quoted
    • Additional compliance options for PII and PHI
    • Responses for 95 percent of PCI SAQ D

Which should you pick?

Choose Affirm if

  • You need pay in 4.
  • You want to start without paying.
  • You work on iOS, Android, Web.
  • You also want monthly instalment loans.
Affirm review

Choose Basis Theory if

  • You need tokenisation api.
  • You work on Web, iOS, Android, Linux.
  • You also want hosted elements.
Basis Theory review

Questions people ask

Is Affirm or Basis Theory better?
Neither clearly leads. Affirm starts at Free and Basis Theory at $995/month, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Affirm or Basis Theory?
Affirm has a free tier; the other does not. Paid plans start at Free for Affirm and $995/month for Basis Theory.
Does Affirm or Basis Theory run on more platforms?
Affirm runs on iOS, Android, Web. Basis Theory runs on Web, iOS, Android, Linux.
Can I use Affirm for free?
Yes. Affirm has a free tier, so you can try it without paying. Basis Theory starts at $995/month.
What is Affirm best used for?
Affirm is most often used for a shopper financing a large purchase such as furniture or electronics who wants disclosed apr terms compared directly against a credit card before committing, someone using the short pay in 4 plan for a smaller purchase who intends to pay it off within six weeks with no interest, a borrower who has missed a payment before and specifically wants a lender that does not charge late fees, a retailer offering point-of-sale financing to reduce cart abandonment on higher-ticket items, in exchange for paying affirm a transaction fee. Of those, a shopper financing a large purchase such as furniture or electronics who wants disclosed apr terms compared directly against a credit card before committing and someone using the short pay in 4 plan for a smaller purchase who intends to pay it off within six weeks with no interest are not what Basis Theory is typically brought in for.
What can Affirm do that Basis Theory cannot?
Affirm covers Pay in 4, Monthly instalment loans, Soft credit check, No late fees. Basis Theory covers Tokenisation API, Hosted elements, Outbound proxy, PCI attestation of compliance.

Answered from the vendors’ own pages

Affirm: Does Affirm always charge interest?

No, short Pay in 4 plans over six weeks are typically interest-free if paid on time; longer instalment plans of three to 36 months can carry a disclosed APR up to roughly 36 percent.

Basis Theory: Does this make us PCI compliant?

It removes cardholder data from your systems and gives you an AOC plus documented responses for most of a SAQ D. Your assessor still determines your scope, and a careless integration can pull systems back in.

Affirm: Does Affirm charge late fees?

No, Affirm does not charge late fees for a missed payment, unlike some buy now pay later competitors, but missed payments can still be reported to credit bureaus.

Basis Theory: What does it cost to start?

995 US dollars a month on Starter, including 20,000 tokens, a production PCI Level 1 environment and US hosting. Higher tiers are quoted.

Affirm: Will using Affirm affect my credit score?

The initial application uses a soft credit check that does not affect your score, but Affirm reports many resulting loans to credit bureaus, so payment history on the loan itself can affect your score.

Basis Theory: Can we switch payment processors without re-collecting cards?

Yes, that is the main non-compliance reason to buy it. You hold the tokens and detokenise into whichever processor you route to.

Basis Theory: Is data stored outside the United States?

Not on Starter, which is US only. Other regions require a Scale or Enterprise agreement.

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