Flagship Merchant Services is one of the largest credit card industry ISOs (independent sales organizations, which act as a 3rd party between a merchant and an acquiring bank that receives the credit card transactions). Under their corporate name of CardServ Inc., they are headquartered in Charleston, MA, and were established in 2001. They focus on payment processing solutions for small- to medium-sized businesses.

First Data is the worldwide leader among credit card processors and electronic payments processors. The company provides services to 6 million merchant locations of all sizes in 80 countries, serves over 7,000 financial institutions and in the most recent reporting year, processed 60 billion transactions. The company processes all payment types, including checks, which are processed through their subsidiary, TeleCheck—their original name and service dating to 1964. First Data is headquartered in Atlanta, Georgia. The New York investment firm, KKR, bought the company in 2007.

Merchant Accounts Express provides merchant credit card processing services, software, and equipment and was established in 1998. They are based in Nashua, New Hampshire. The company is also identified with the names Merchant Express and ME Acquisitions, LLC.

Merchant One is a registered ISO/MSP (Independent Sales Organization/Member Service Provider) of Wells Fargo Bank, NA Walnut Creek, California, and of First National Bank of Omaha, Omaha, Nebraska. Merchant One was established in 2002 and is based in Miami Beach, Florida.

Since 2003, The Transaction Group (TTG) has been dedicated to low-cost payment processing solutions. They act primarily as an independent agent of PowerPay, a Portland, Maine, based registered ISO/MSP (Independent Sales Organization/Member Service Provider) of: HSBC Bank USA National Association, Buffalo, NY, and BancorpSouth, Tupelo, MS. Certain other affiliates are used for Canadian businesses and those high-risk. MLR Marketing Group Inc. operates as The Transaction Group and is headquartered in Jacksonville Beach, Florida.

Leaders Merchant Services is headquartered in Camarillo, California, and has been operating since 2000. They are an ISO/MSP (Independent Sales Organization/Member Service Provider) of Wells Fargo Bank and offer a full range of credit card processing and transaction services and equipment for home-based, retail, mail & telephone order, and Internet e-commerce.

Privately-owned and Boston, Massachusetts-based Merchant Warehouse was established in 1998. They are an ISO/MSP (Independent Sales Organization/Member Service Provider) and have a commitment to excellence in pricing, service, and customer satisfaction. Some 30,000 new merchants are added to their roster yearly. In their last reporting period, they processed some $7 billion a year in sales, and over 9 million transactions a month.

The origins of Gotmerchant.com date to 1998. Formerly in a referral partnership, they themselves became a direct seller of credit card processing services in 2003 in order to maintain a commitment to a high standard of customer care and service in which they excel. They are headquartered in Denton, Texas, and are an ISO/MSP (Independent Sales Organization/Member Service Provider) through HSBC Bank.