What a racket!

The United States Tennis Association cheated the city out of more than $300,000 in rent by under-reporting its revenues by at least $31 million, according to a blistering report by the City Comptroller released as the organization holds its famed US Open event.

The undercount from 2014-2017 means that the USTA owes the city at least $311,000 from its operation of the sprawling Billie Jean King National Tennis Center at the Flushing Meadows Park in Corona.

Additionally, the Comptroller’s Office said its review found additional evidence that USTA potentially failed to report an additional $8 million in revenue, which could bring the undercount up to $39 million.

“An organization as revenue rich as the USTA should not be fudging its finances and should not be nickel and diming New York City,” said Comptroller Scott Stringer at a Thursday press conference. “But they are, and it’s at New York City’s expense.”

The watchdog discovered the undercounting during a routine audit of the deal, officials said.

Stringer’s office released the report during the opening week of the US Open, the USTA’s premier annual tournament at the Tennis Center.

Under its deal with the city, USTA must pay $400,000 in annual rent plus 1% of revenues when the Tennis Center complex generates more than $20 million in receipts.

“When you underreport income and you don’t give the money that’s owed to the city, who are you hurting here,” asked Stringer. “You’re hurting the children, you’re hurting people in communities.”

The Comptroller’s Office also scalded the Parks Department for failing to properly oversee the 99-year lease that allows the USTA to operate the tennis center, finding the agency often accepted UTSA’s financial statements at “face value.”

“While we will be taking the recommendations from the report under advisement, we continue to maintain a positive relationship with [the tennis center],” Parks spokeswoman Meghan Lalor said.

Parks officials also said that the USTA has paid back half of the owed revenue, $143,297.

“We were incredibly cooperative,” said Danny Zausner, a top USTA official at the Tennis Center, when asked for comment. “That he chose the US Open period to grandstand about miscellaneous things is disappointing.”

He said the organization disputes the Comptroller’s findings and only believes they owe roughly half of the money — which the Parks Department confirmed it received a check for.

“They’re entitled to their opinion, but we don’t necessarily agree with it,” Zausner said.

But, he added: “When we’re wrong, we’re wrong and to some of these things we’ve agreed to make changes.”