Visa handles more than 60% of debit card transactions in the U.S., and collects more than $7 billion in annual processing fees—a lucrative business the company protects through illegal, anticompetitive practices,

According to the complaint, Visa entered into paid agreements with potential competitors as part of an effort to fend off competition from newer entrants into the payment processing industry. These practices have allowed Visa to build an “enormous moat” around its business, the complaint alleges.

The Justice Department is accusing Visa of running a debit card monopoly that has hiked fees for American consumers and businesses.

Visa’s heft in the market has allowed it to pressure merchants into accepting its cards to avoid steep costs on billions of dollars of transactions, the DOJ says.

The U.S. Justice Department on Tuesday sued Visa, the world’s biggest payments network, saying it propped up an illegal monopoly over debit payments by imposing “exclusionary” agreements on partners and smothering upstart firms.

The Department of Justice (DOJ) filed an antitrust lawsuit against Visa. The lawsuit alleges that the financial firm holds a monopoly over debit network markets allowing it to charge banks and markets with exorbitant fees that get passed onto consumers and keep rival companies like PayPal and Square from competing on their level.

The complaint says Visa penalizes merchants and banks who don't use its own payment processing tech to process debit transactions.

The Justice Department filed a lawsuit against Visa on Tuesday, alleging the financial services giant used its clout to maintain a monopoly over the U.S. debit card market.