Merchant card processing is the network of technology and financial infrastructure that kicks into gear whenever a customer makes a card payment. It involves verifying the card info, checking for funds, and moving money from the customer’s bank account to yours—all behind the scenes.
For JW Wiseman, founder of Curious Elixirs, using a merchant card processing provider was transformational. He says on the Shopify Masters podcast, “Shop Pay has been absolutely incredible not only as a business owner, but also as a consumer of different products. It makes it so much easier to say yes, to try something out. It’s transformative for people who are trying to get customers to try their product for the first time.”
This guide walks you through how merchant card processing works, the key players involved, and best practices for keeping payments secure and efficient.
What is merchant card processing?
Merchant card processing is the system that allows you to accept any type of card payment, whether the transaction is online or in-store. It encompasses more than credit card transactions because it includes credit and debit cards, prepaid cards, and digital wallets such as Apple Pay and Google Pay.
When a customer shares their card details, a payment processor verifies the card information, checks that funds are available, and completes the transaction.
Five key parties work together to make that happen:
-
The merchant. You accept payment for a product or service.
-
The customer. They can swipe, tap, or insert a card at a terminal, or they write or type in their card details.
-
Your payment processor. This service handles the technical side, passing transaction data between you, the card networks, and the banks involved.
-
Card networks. Visa, Mastercard, American Express, and other networks route the transaction and set the rules for how it moves.
-
The issuing bank. Your customer’s bank or card issuer approves or declines the payment and transfers the funds.
How does merchant card processing work?
From the moment a customer pays to when funds land in your account, a card transaction moves through four key stages: authorization, capture, clearing, and funding. Here’s what happens at each step:
Authorization
Once a customer initiates payment, the payment gateway sends an authorization request to the payment card network, which routes it to the customer’s card issuer. The issuer verifies the card is valid, checks for fraud signals, and confirms the customer has enough funds or available credit to cover the purchase.
For in-person purchases, authorization happens when the customer taps, swipes, or inserts their card in the payment terminal. For online purchases, it happens as soon as the customer enters their payment information and places the order.
The information flows back to the payment processor, and the payment is approved or declined. The process usually takes just a few seconds.
Capture
When the merchant is ready to receive the funds, they’ll “capture” payment. This process tells the customer’s bank it’s time to transfer the funds into the merchant’s account.
In retail stores, authorization and capture often happen automatically at the point of sale. For online orders, merchants may wait until an item ships to capture the payment, especially if products are backordered or sold in multiple shipments.
Clearing
After capture, the payment information moves through the card network, such as Visa, Mastercard, or American Express. The network verifies the transaction and calculates how much of the processing fee goes to each party. The card issuer, acquiring bank, and payment processor usually each charge a fee.
Funding
Once the transaction clears, the funds are transferred from the issuing bank to the merchant’s account, minus any applicable credit card processing fees. Merchants may receive payouts as soon as the same day or after a few business days. The timeline depends on the payment processor.
Best practices for merchant card processing
- Offer multiple payment methods
- Use secure payment technologies
- Optimize checkout
- Monitor payment performance over time
Here are a few practices that can help you improve sales, protect against fraud, and keep payments running efficiently:
Offer multiple payment methods
According to Baymard data, some 9% of would-be buyers abandon their shopping carts when the merchant doesn’t offer sufficient payment flexibility, such as:
-
Digital wallets like Apple Pay, Google Pay, and Shop Pay
-
Major credit cards
-
Cash and checks
-
Local payment methods if you sell internationally
Shopify provides a range of payment methods that work no matter where you’re selling. Whether you’re using card reader terminals, Shopify POS, or Tap to Pay, all transactions flow into the same unified sales and inventory data system, and sync automatically.
Use secure payment technologies
Every dollar of fraud costs US retailers $4.61, according to the 2025 LexisNexis True Cost of Fraud study, making it crucial for merchants to protect their businesses while building customer trust. To that end, look for payment processing solutions that include:
-
PCI DSS compliance built into the platform
-
End-to-end encryption and tokenization for stored payment data
-
Fraud analysis tools that flag suspicious orders before they’re fulfilled
-
EMV chip and contactless support for in-person transactions
Shopify Payments builds these fraud prevention features directly into the platform. The same security standards apply whether a transaction happens through your online store, a card reader, or Tap to Pay, so you’re not managing different compliance requirements across channels.
Optimize checkout
A complicated or slow checkout is another way to lose out on sales, with 17% of visitors abandoning their carts for this reason, according to Baymard. Ways to optimize your online checkout include:
-
Minimizing form fields
-
Offering guest checkout
-
Enabling one-click payment options
-
Ensuring your checkout page loads quickly on mobile devices
Shop Pay, an accelerated checkout option, saves a customer’s email, payment method, and shipping and billing details, so they don’t have to re-enter them on future purchases. It boosts conversion by up to 50% compared to guest checkout.
It’s also possible to speed up the checkout process beyond the browser. With Shopify POS and supported card readers, customers can choose to tap a card, phone, or smartwatch instead of inserting or swiping. In-person payments sync automatically with your online store, so there’s no manual reconciling.
Monitor payment performance over time
Payment processing isn’t a set-it-and-forget-it decision. Make it a habit to regularly review:
-
Payment workflows. Are there unnecessary steps or failure points in how transactions are authorized and captured?
-
Settlement timing. How quickly are funds actually reaching your bank account, and does that match your cash flow needs?
-
Processing costs. Are you paying competitive rates, and are there hidden fees from third-party gateways eating into margins?
Shopify Payments simplifies this ongoing review because it’s a built-in processing solution. There’s no separate gateway to configure, and it eliminates third-party transaction fees that apply when using external payment providers on Shopify.
Merchant card processing FAQ
What is the difference between a payment processor and a payment gateway?
A payment gateway and payment processor serve two different functions at checkout. The payment gateway is a tool that allows merchants to securely accept payments online. The payment processor is a business that partners with the merchant to facilitate customer payments, both online and in person. It does the work of verifying transaction details, ensuring the customer has enough funds, approving or denying transactions, and moving money between banks.
What is the difference between card-present and card-not-present transactions?
Card-present transactions happen when a customer physically taps, inserts, or swipes their card or mobile wallet at a store using a payment terminal. A card-not-present transaction happens when a credit card isn’t physically presented to the merchant at checkout.
Can businesses accept both online and in-person card payments?
Yes, accepting credit card payments online and in-person is common, but having the right merchant services provider can help make it easier and expand the types of cards you can process. With Shopify, for instance, in-store sales through POS and supported card readers sync with your online store, so your inventory, order history, and customer data stay in one place no matter where a sale happens.
