Merchant Credit Card Processing: How It Works

Key Takeaways

• Every card transaction involves four parties: the cardholder, the issuing bank, the card network, and the acquiring bank. The payment processor sits between the merchant and the acquiring bank.
• Interchange is the fee paid to the cardholder's issuing bank on every transaction. It is the largest component of credit card processing costs, typically 1.5% to 2.1% for consumer credit cards and lower for debit cards.
• Flat-rate pricing bundles interchange, network fees, and processor margin into a single rate (typically 2.9% + $0.30 for online transactions). It is simple but typically more expensive for high-volume businesses.
• Interchange-plus pricing charges actual interchange plus a small fixed processor markup. It is more complex but significantly cheaper at scale. A business processing $1M per year can save $5,000 to $15,000 annually by switching from flat-rate to interchange-plus.
• The card type the customer uses determines the interchange rate. A premium rewards card or business card carries higher interchange than a basic debit card, meaning the merchant pays more when a customer pays with a rewards card even on the same card network.

What Is a Merchant Credit Card Account?

A merchant credit card account, often called a merchant account, is an agreement between a business and an acquiring bank or payment processor that authorizes the business to accept card payments. The merchant account holds funds in transit between the point of sale and the deposit to the business's operating bank account, typically for one to two business days.

Historically, every business needed a dedicated merchant account from a bank to accept cards. Modern payment processors like Stripe, Square, and PayPal aggregate many merchants under a single master merchant account, which is why they can onboard merchants in minutes rather than the days or weeks a traditional bank merchant account required. The trade-off is that aggregated accounts have less pricing flexibility and fewer customization options than dedicated merchant accounts.

The Four Parties in Every Card Transaction

According to UCSB's card processing terminology guide, every credit card transaction involves four distinct parties whose interactions determine how the transaction is authorized, settled, and what fees are charged.

The cardholder is the customer initiating the payment with their credit or debit card.

The issuing bank is the cardholder's bank: the institution that issued the card and extends credit to the cardholder. When a transaction is authorized, the issuing bank checks the cardholder's available credit and approves or declines. At settlement, the issuing bank transfers funds to the card network minus the interchange fee it retains.

The card network (Visa, Mastercard, American Express, or Discover) operates the infrastructure connecting all banks, sets the interchange fee schedules, and establishes the rules that govern dispute resolution and chargebacks. American Express historically both issued cards and operated as the network, though its model has evolved.

The acquiring bank is the merchant's bank. It receives settlement funds from the card network and deposits the net amount to the merchant's account after deducting the discount rate.

The payment processor is not one of the four core parties but sits between the merchant and the acquiring bank, handling the technical transmission of transaction data. In many modern setups, the processor and acquiring bank function are combined in a single provider.

Merchant Credit Card Fees: What You're Actually Paying

The total cost of accepting a card payment has three components that are bundled together differently depending on the pricing model.

Interchange is the fee paid to the cardholder's issuing bank. It is set by the card network and varies by card type, transaction type, and how the card is accepted. Interchange is the largest component of card processing costs and the one the processor has no control over. When a processor charges a merchant a processing rate, a significant portion of that rate is passed through to the issuing bank as interchange.

Network fees (also called assessment fees or scheme fees) are paid to the card network itself for operating the infrastructure. These are typically small, around 0.13% to 0.15%, and relatively consistent across card types on the same network.

Processor markup is the fee the payment processor retains for its service. This is the component that varies between processors and pricing models, and its the only component that is actually negotiable.

Flat-Rate vs Interchange-Plus: The $9,000 Question

This is the pricing distinction most founders never encounter until alot of money has already left through the difference.

Flat-rate pricing combines interchange, network fees, and processor markup into a single blended rate. Stripe charges 2.9% plus $0.30 for online card transactions. Square charges 2.6% plus $0.10 for in-person transactions. The rates are transparent, predictable, and require no knowledge of interchange to understand a monthly statement.

The cost is that the processor earns margin on the spread between actual interchange and the flat rate. When a customer pays with a basic Visa debit card carrying interchange of approximately 0.05% plus $0.22 (for regulated debit under Durbin Amendment limits), the processor collects 2.9% and passes through a fraction of that. On a $100 transaction, the processor collects $2.90 and passes approximately $0.27 as interchange, retaining $2.63. The merchant pays 2.9% regardless of actual card cost.

Interchange-plus pricing charges the actual interchange rate on each transaction plus a fixed processor markup, typically 0.2% to 0.5% plus $0.05 to $0.15 per transaction. The merchant sees exactly what interchange was charged on each transaction and pays a consistent markup on top.

A business processing $1M per year with an average interchange rate of 1.8% on interchange-plus at a markup of 0.3% plus $0.10 per transaction pays an effective rate of approximately 2.1% plus per-transaction fees. The same volume on flat-rate at 2.9% costs $29,000. The interchange-plus scenario costs approximately $21,000 on the percentage component. The $8,000 difference stays with the business. Interchange-plus pricing is available from most full-service processors and most merchant acquirers. It is rarely the default option because it requires the merchant to ask.

Why the Same Card Network Produces Different Fees

Not all Visa cards cost the same to accept. The interchange rate is determined by the card type, not just the card network, which means a merchant can pay significantly different fees on two transactions of identical size on the same network.

A standard Visa debit card carries lower interchange (regulated by the Durbin Amendment for banks with over $10 billion in assets). A Visa Signature or Visa Infinite premium rewards card carries interchange of approximately 2.1% plus $0.10. A Visa business card carries still different interchange based on whether its processed as a consumer or commercial card.

When a customer pays with a premium rewards card, the merchant subsidizes the cardholder's rewards program through higher interchange. The merchant has no control over which card the customer uses and no visibility into the interchange variation under flat-rate pricing. Under interchange-plus pricing, the variation is visible on the statement but not controllable.

This is why high-ticket B2B businesses where customers frequently use corporate or business cards pay more in effective interchange than consumer-facing businesses where customers more often use basic debit cards. Understanding this helps founders evaluate whether card acceptance costs are in line with what the underlying card mix should produce.

Payment Technology: How Card Transactions Move

The physical or digital movement of a card transaction follows a defined sequence. Authorization happens in near real time: the merchant's terminal or payment gateway transmits transaction data to the processor, which routes it to the card network, which forwards it to the issuing bank. The issuing bank approves or declines within seconds and the response returns through the same chain.

Settlement happens in batch, typically end of day. The merchant's processor submits all authorized transactions to the card network, which nets out the interchange and distributes funds to the acquiring bank, which deposits the net amount to the merchant's account one to two business days later.

The gap between authorization and settlement is why card fraud creates a merchant problem. An authorized transaction that is later identified as fraudulent can be charged back after the settlement has already cleared, requiring the merchant to return the funds.

Card Processing and Your Books

Every card settlement that hits the merchant's bank account needs to land correctly in QuickBooks Online, categorized as revenue in the period the sale occurred rather than the period the batch settled. For businesses using Stripe, keeping QuickBooks Online and Stripe connected for real-time transaction visibility ensures card revenue is recorded at the invoice and transaction level rather than as aggregate daily deposits that require manual matching.

Finlens runs on top of QuickBooks Online with no migration and automates the categorization that keeps card processing revenue accurate in the books as settlements arrive.

FAQ

What is a merchant credit card account?‍

A merchant credit card account is a commercial arrangement that allows a business to accept credit and debit card payments. It holds funds in transit between the point of sale and the deposit to the business's operating bank account.

What is interchange in credit card processing?

‍Interchange is the fee paid to the cardholder's issuing bank on every card transaction. It is set by the card network and varies by card type. It is the largest component of credit card processing costs, typically 1.5% to 2.1% for consumer credit cards.

What is the difference between flat-rate and interchange-plus pricing?

‍Flat-rate pricing charges a single blended rate regardless of card type (for example, 2.9% plus $0.30). Interchange-plus pricing charges the actual interchange rate on each transaction plus a fixed processor markup. Interchange-plus is typically cheaper for high-volume businesses but requires understanding interchange variation.

Why do different cards produce different processing fees?

‍The interchange rate varies by card type. A premium rewards card carries higher interchange than a basic debit card even on the same network. When a customer pays with a rewards card, the merchant pays higher interchange to fund the cardholder's rewards program.

What is a payment processor?

‍A payment processor handles the technical transmission of card transaction data between the merchant and the acquiring bank. Modern processors like Stripe and Square combine payment processing with acquiring bank functions and merchant account management in a single product.

What is a chargeback?

‍A chargeback is a reversal of a card transaction initiated by the cardholder's issuing bank at the cardholder's request. Chargebacks return funds to the cardholder and deduct them from the merchant's account. They occur when a cardholder disputes a transaction as fraudulent, unauthorized, or undelivered.