Apple is seeking monetary damages to compensate for its loss of fees, according to a filing Tuesday in federal court in Oakland, Calif.. Epic last month launched a payment system that circumvented the Apple App Store, so the iPhone maker didn’t get a cut of purchases inside of Fortnite. Apple stopped new users from downloading Fortnite on its platform in August, but existing copies of Fortnite can still use Epic’s system.

Epic sued Apple on Aug. 13, claiming the removal of the Fortnite app from the App Store is “retaliation” for the game maker’s decision to offer in-app purchases through its own marketplace. Epic was denied a court order that would have temporarily stopped Apple from delisting Fortnite. Epic didn’t immediately respond to a request for comment.

The case is shaping into a major antitrust battle over tolls of as much as 30% that Apple charges developers when users make in-app purchases. Epic has filed a separate suit with similar claims against Google.

Apple said in Tuesday’s filing that Epic’s actions have hurt its business and customer relationships. “Epic’s conduct actually interfered with Apple’s relationships with its consumers, in particular those who made purchases through Epic’s unauthorized external purchase mechanism, by depriving Apple of the economic benefit that it reasonably expected to receive from those relationships,” Apple said in its filing.

Contradicting Epic’s claim that the App Store is anti-competitive, Apple said the store provides a service and helps developers make money.

More than $116 billion of the App Store’s 2019 sales of almost $140 billion “went entirely into app developers’ back pockets,” Apple said.