Acquiring and Processing

The merchant's side of the equation, and the infrastructure that makes acceptance possible.

In Module 1, we traced the full lifecycle of a card transaction and identified five core actors. The acquirer sat in the middle of that chain, routing authorisation requests and receiving settled funds on behalf of the merchant. That was the simplified view.

In practice, the acquiring side of payments is where much of the industry's complexity lives. The merchant does not simply "have an acquirer." They have a stack of relationships: a gateway that captures transactions, a processor that routes messages, and an acquirer that holds the settlement account and bears the financial risk. Sometimes these are three separate companies. Sometimes they are one. Knowing the difference matters.

This module breaks open the acquiring side. We will define the three core roles, explain how merchant onboarding and underwriting work, map the different pricing models, and explore why the lines between gateways, processors, and acquirers are blurring.

If Module 1 was the anatomy of a transaction, Module 2 is the anatomy of the merchant's payments infrastructure. Every company in this space is fighting for a position in this stack.

Gateway, Processor, Acquirer: Three Roles, One Stack

The acquiring side of a card transaction involves three distinct functions. They are often confused because some companies perform all three, but the roles themselves are different. Understanding where one ends and the next begins is essential for anyone building, selling, or buying payments infrastructure.

The Payment Gateway

The gateway is the merchant's front door to card acceptance. It sits between the merchant's website, app, or point-of-sale terminal and the rest of the payments infrastructure. Its job is technical: capture the card data, encrypt it, tokenise it where required, format it into a properly structured authorisation request, and pass it downstream.

In e-commerce, the gateway is what powers the checkout page. When a customer enters their card details on a website, those details hit the gateway first. The gateway handles PCI compliance (keeping raw card numbers out of the merchant's environment), supports multiple payment methods, and provides the API that developers integrate against.

Key gateway providers include Stripe, Braintree (owned by PayPal), Adyen, Checkout.com, and legacy players like Worldpay's gateway products. In the physical world, the terminal manufacturer (like Ingenico or Verifone) often provides gateway-equivalent functionality.

The Payment Processor

The processor is the message router. It takes the formatted authorisation request from the gateway and sends it to the correct card network using the appropriate message standard (ISO 8583 today, increasingly ISO 20022 in the future). It also handles the clearing and settlement messaging: batching transactions, submitting them to the network, and receiving the settlement files back.

Processing is a scale business. The infrastructure required to maintain direct connections to Visa, Mastercard, and other networks, handle millions of messages per second, and maintain five-nines uptime is significant. This is why processing tends to consolidate. Major processors include Fiserv (First Data), FIS (Worldpay), Global Payments (TSYS), and Adyen (which processes in-house).

The Acquirer

The acquirer is the financial institution that sits behind the processor and the gateway. It holds the merchant's settlement account, underwrites the merchant (deciding whether to accept the risk of processing their transactions), and bears the financial liability if something goes wrong. If a merchant goes bankrupt and cannot cover its chargebacks, the acquirer is on the hook.

Acquiring is a regulated activity. In most jurisdictions, the acquirer must be a licensed financial institution or a registered member of the card networks. This is a significant barrier to entry. Companies like Stripe and Square initially operated as payment facilitators (PayFacs) under a sponsoring acquirer's licence before obtaining their own.

The gateway is a technology problem. The processor is an infrastructure problem. The acquirer is a financial risk problem. The same transaction touches all three, but the skills, capital, and regulatory requirements at each layer are completely different.

When the Lines Blur

The clean separation of gateway, processor, and acquirer is how the industry was structured for decades. It is no longer how most of it works. The dominant trend in payments over the past 15 years has been vertical integration: companies expanding from one layer into all three.

The direction is clear. Companies that started as gateways are building or acquiring processing and acquiring capabilities. Companies that started as processors are adding gateway and merchant-facing layers. The economic logic is simple: owning more of the stack means capturing more of the fee, reducing dependency on partners, and controlling the merchant relationship.

This matters for merchants because it affects pricing, flexibility, and lock-in. A fully integrated provider offers simplicity (one contract, one dashboard, one integration). A best-of-breed approach (separate gateway, processor, and acquirer) offers flexibility and potentially better pricing at scale, but at the cost of complexity.

The Payment Facilitator Model

Not every merchant has a direct acquiring relationship. In fact, most small merchants do not. They use a payment facilitator, or PayFac.

A PayFac is a company that aggregates merchants under its own master merchant account with an acquirer. Instead of each merchant going through individual underwriting and getting their own merchant ID (MID), the PayFac onboards them as sub-merchants under a single umbrella. This dramatically simplifies and speeds up the onboarding process.

Stripe, Square, PayPal, and Shopify Payments are all payment facilitators (or were, before some obtained full acquiring licences). The model works because the PayFac takes on the underwriting burden and the risk. In exchange, they charge a markup on the processing fee. The merchant gets fast, simple onboarding. The PayFac gets control of the merchant relationship and a recurring revenue stream.

The trade-off is cost. At low volumes, the convenience of a PayFac is worth the premium. As merchants grow and their transaction volume increases, the economic case for moving to a direct acquiring relationship (with interchange-plus pricing) becomes stronger. This transition point, often somewhere between $5 million and $50 million in annual volume, is one of the most important commercial decisions a growing business makes.

Merchant Onboarding: From Application to Live

Before a merchant can accept their first card payment, they must be onboarded and underwritten. This process varies dramatically depending on whether the merchant is using a PayFac or going through traditional acquiring, but the underlying checks are similar.

For a PayFac like Stripe, this process can take minutes. For traditional acquiring with a bank, it can take days or weeks. The FDIC recently clarified its supervisory approach to payment processing relationships, signalling that regulators are paying closer attention to how acquirers and PayFacs manage merchant risk, particularly for merchants in higher-risk categories.

Onboarding speed is one of the most powerful competitive advantages in payments. The companies that can say "yes" fastest, while still managing risk effectively, win the merchant relationship.

Pricing Models: How Merchants Pay

Every merchant pays fees to accept card payments. How those fees are structured varies, and the model matters enormously for the merchant's bottom line. There are three dominant pricing approaches.

Interchange-Plus (IC+)

The most transparent model. The merchant pays the actual interchange fee (set by the card network and varying by card type, transaction type, and region) plus a fixed markup from the acquirer/processor. The merchant sees exactly what interchange they are paying and what the processor is charging on top.

Interchange-plus is the industry standard for mid-market and enterprise merchants. It rewards merchants who optimise their transaction mix (using lower-interchange card types and transaction methods) and gives them full visibility into their costs.

Blended (Flat Rate)

The merchant pays a single, fixed percentage on every transaction regardless of the underlying interchange rate. Stripe's standard 2.9 percent + $0.30 and Square's 2.6 percent + $0.10 are blended rates.

Blended pricing is simple and predictable. The merchant knows exactly what they will pay per transaction. The trade-off is cost: the processor sets the blended rate high enough to cover the most expensive interchange categories (rewards cards, international cards), which means merchants processing mostly debit cards or domestic transactions are overpaying relative to interchange-plus.

Tiered

The oldest and least transparent model. Transactions are sorted into "qualified," "mid-qualified," and "non-qualified" tiers, each with a different rate. The problem is that the acquirer defines which transactions fall into which tier, and these definitions are often opaque. A transaction that the merchant expects to be "qualified" might be downgraded for reasons that are difficult to understand or predict.

Tiered pricing is declining but still exists, particularly among legacy acquirers and ISO (Independent Sales Organisation) channels. It is almost always more expensive than interchange-plus for merchants who take the time to compare.

Pricing is where the acquiring relationship becomes a commercial negotiation. The model a merchant chooses, or is offered, directly shapes their unit economics. For high-volume businesses, the difference between blended and interchange-plus can be hundreds of thousands of dollars per year.

Risk and Reserves: The Acquirer's Exposure

Acquiring is a risk business disguised as a technology business. The acquirer sits between the merchant and the card networks, and when things go wrong, the acquirer is financially liable.

The primary risks an acquirer manages are:

• Chargeback exposure. If a merchant generates chargebacks that exceed their deposits, the acquirer absorbs the loss. This is why acquirers scrutinise merchants with high chargeback rates or in high-risk industries.
• Merchant insolvency. If a merchant accepts payments for future delivery (travel, events, subscriptions) and then goes bankrupt, cardholders dispute those charges. The acquirer pays.
• Fraud losses. Authorised push payment fraud, card testing, and transaction laundering all create financial exposure for the acquirer.
• Regulatory fines. Card networks impose fines on acquirers whose merchants breach scheme rules. Excessive chargebacks, data breaches, or prohibited activity can trigger penalties that flow to the acquirer.

To manage these risks, acquirers use several tools:

• Rolling reserves. A percentage of the merchant's settlement (typically five to ten percent) is held back for a period (90 to 180 days) as a buffer against future chargebacks.
• Delayed settlement. Instead of settling on T+1, higher-risk merchants may receive funds on T+7 or longer, giving the acquirer time to identify problems.
• Volume caps. Limits on the total amount a merchant can process per day or month until they build a track record.
• Monitoring programmes. Automated systems that flag unusual patterns: sudden volume spikes, changes in average transaction value, or geographic anomalies.

The best acquirers say "yes" to more merchants by managing risk more intelligently, not by ignoring it. The tools they use to do this (reserves, monitoring, dynamic limits) are as important to understand as the transaction flow itself.

ISOs, ISVs, and the Distribution Layer

Not every merchant buys payments directly from an acquirer or a PayFac. Between the acquiring infrastructure and the merchant, there is an entire distribution layer.

The ISV channel is where much of the growth in merchant acquiring is happening. When a restaurant installs Toast's POS system, payments are embedded. When a retailer uses Shopify, payments are embedded. The merchant is not choosing a payment processor. They are choosing software, and the software has chosen the processor for them.

This has major implications. The company that controls the software relationship controls the payment routing decision. This is why Fiserv, Global Payments, and others are investing heavily in ISV partnerships and embedded payments platforms. Whoever owns the software layer owns the distribution.

The Acquiring Value Chain: Where the Money Goes

The economics of acquiring are straightforward at a high level. Interchange goes to the issuer. Scheme fees go to the network. Everything else is split among the companies on the merchant's side: the gateway, the processor, the acquirer, and any intermediaries (ISOs, ISVs, PayFacs). On interchange-plus pricing, the acquiring-side margin is thin. On blended pricing, it can be substantial.

This is why blended-rate companies like Stripe and Square can generate strong gross margins despite appearing to charge "only" 2.9 percent. The spread between interchange and the blended rate is their revenue. The challenge is retaining merchants as they scale and become sophisticated enough to demand interchange-plus pricing.

Glossary