The merchant's bank in a card payment. It signs up the business, routes each sale for approval, settles the money into the merchant's account - and owns the risk when things go wrong.
01 · Where it sits in one card swipe
Gateway and processor sit between the merchant and the acquirer - a "payment processor" isn't a rebrand of the acquirer, it's a distinct technical layer the acquirer relies on. Of every party in the chain, the acquirer is the only one working for the merchant.
02 · Gateway, processor, PSP - how the terms actually map
Are these terms interchangeable? No. Gateway, processor, and acquirer are three distinct functions, each doing a different job in the chain above. "PSP" and "full-stack" are not a fourth function - they're commercial packaging labels describing how many of those functions one company bundles into a single merchant-facing product. Every full-stack provider is a PSP; not every PSP is full-stack.
The three functions, and what each bundle actually covers underneath one merchant bill:
The connectivity layer between checkout and the rest of the chain. It encrypts the transaction at checkout and routes it to a processor or acquirer. A gateway doesn't hold merchant funds or take on settlement risk - it's connectivity, not banking.
The technology layer that runs authorization and settlement logic on the acquiring bank's behalf. It's not the bank itself, and it's not the pipe that reaches it - often the same company as the acquirer, or a close technology partner operating under its license.
A commercial packaging label, not a fourth function. A PSP wraps gateway, processing, and often the acquiring relationship itself into one product, so a merchant can start accepting cards without negotiating its own bank relationship. Some PSPs hold their own acquiring license and run full-stack; others partner with a bank acquirer behind the scenes.[1]
Adyen holds direct acquiring licenses across 30+ markets; Stripe's US MALPB charter (approved 2025) added direct network membership on top of its historical aggregator model, per SBS Software.
The merchant sees one bill - but underneath it, gateway, processor, acquirer, and network are frequently four separate companies, or one company wearing four hats.
03 · Encryption: the card number is never in the open
Card data is locked at the terminal (P2PE) and swapped for a token. The real number is only unlocked inside the acquirer's secure vault - a hardware security module no person can read from.
04 · Cross-border: where you acquire changes the outcome
A local acquirer processes the sale inside the customer's market instead of routing it abroad. The transaction looks domestic to the issuer - so it clears more cleanly.
05 · Financial impact: who gets paid out of one sale
Interchange typically represents 70 to 90% of total card acceptance costs, per Wikipedia's interchange fee overview. Settlement timing framework per PXP; acquirer chargeback liability per FasterCapital.
Of five parties in a card sale, the acquirer is the only one whose job is to get the merchant paid.
06 · How acquirers actually make money
The interchange-plus margin above is the acquirer's core revenue line, typically 10 to 30 basis points over pass-through interchange and scheme costs.[1] But most acquiring relationships layer several other charges on top, some tied to volume, some fixed no matter how much a merchant processes.
Fee structure per Checkout.com and PXP. Rate ranges: statement fees $5 to $15/mo, PCI compliance $5 to $15/mo for a compliant merchant, chargebacks $15 to $25 per dispute, gateway access $10 to $25/mo, cross-border network assessments 0.4% to 1.4% plus an FX markup of 1% to 3%.
Illustrative only, not a real property. Assumptions: 95 rooms, $92 ADR and 62% occupancy (in line with national midscale benchmarks of roughly $86 ADR at 54.5% occupancy[3]), and 92% of guest folios settled by card. That's about $162,600 in monthly room revenue and roughly $149,600 in monthly card volume flowing through the acquirer.
That's roughly 0.38% of card volume on top of pass-through interchange and scheme fees, a normal range for a full-service midscale property. A limited-service property with fewer folio adjustments and lower international mix would land toward the low end; a property running a heavier OTA or group mix would run higher on chargebacks and cross-border.
07 · Where the function is headed
The line between "PSP" and "acquirer" is dissolving - the companies that control the full stack are the ones setting the economics.
Adyen holds direct acquiring licenses across 30+ markets, connecting straight to Visa, Mastercard, and local networks with no sponsoring bank in between. Stripe historically ran as an aggregator under a partner bank's license; in 2025 its Merchant Acquirer Limited Purpose Bank (MALPB) charter was approved in Georgia, giving it direct US network membership for the first time.[4] Each additional license a PSP holds is margin and risk control it no longer shares with a bank partner.
Software platforms increasingly become the merchant of record for their own sub-merchants via tools like Stripe Connect or Adyen for Platforms, pushing the traditional acquirer another layer from the end business. Stripe Connect charges a monthly fee per active connected account, so cost compounds as a platform's merchant base grows; Adyen for Platforms is slower to onboard but its pricing scales better above roughly $50M in transaction volume.[5]
Real-time account-to-account systems are starting to route some transactions around card networks entirely. Brazil's Pix processes roughly 3.8 billion transactions a month at an average cost near $0.004 per transfer; India's UPI clears more than 12 billion transactions a month. The US FedNow network is far earlier in adoption, growing from 35 launch participants in July 2023 to 400+ participants by March 2026.[6] None of the three touch a card network, an issuer, or an acquirer in the traditional sense.
Automated risk scoring is compressing merchant onboarding from weeks to minutes: industry reporting puts instant approval rates for standard digital merchant applications at roughly 92%, with AI agents auto-approving 60 to 75% of low-risk applications without a human underwriter and cutting onboarding time from days to hours.[7] The acquirer's traditional gatekeeping role - manually reviewing every new merchant - is loosening as a result.
I write about payments infrastructure from 15+ years across American Express, Fidelity, Starwood, and Wyndham. Let's talk. I'm always open to consulting projects, contract work, or Senior Management/Director level roles in travel and payments, and to advisory discussions on programs navigating topics like this.
Get in touchEducational use only; not affiliated with any card network or acquirer. Fee proportions are illustrative and vary by card type, region, and pricing model. The hotel example in Section 06 is a hypothetical illustration, not a real property. Sources: PXP, Merchant Discount Rate · Checkout.com, interchange fees explained · Chargeback Gurus, understanding MDR · Wikipedia, interchange fee · In Practise, Adyen/Stripe/Checkout.com · SBS Software, PSP credit institution licenses · PXP, settlement timing · FasterCapital, acquirer chargeback liability · Verisave, merchant account fees · Paytia, PCI compliance cost · Chargebacks911, chargeback fees · payabl., gateway fees · Clearly Payments, cross-border fees · Oysterlink, hotel ADR benchmarks · Ryft, embedded payments comparison · PaySpace Magazine, A2A payment statistics · Payabli, AI merchant onboarding. June 2026