Nikita Mazepin has announced he is suing Haas over "salary arrears" that he says are owed for the 2022 season.
The Russian driver was axed by Haas on the eve of the new Formula One season following Russia's invasion of Ukraine, which also saw F1 cancel the Russian Grand Prix in Sochi.
Haas cancelled their title sponsor deal with Russian fertilizer company Uralkali, owned by Nikita's father Dmitry, and replaced Mazepin with Kevin Magnussen for the 2022 season.
Mazepin's relationship with Haas has soured since his contract was terminated in March, with the driver claiming his wish to continue racing by accepting the FIA's regulations for Russian drivers was ignored.
He has alleged he only found out about the termination via Haas' press release and is now set to take the team to court – though he made it clear this would be a "personal matter" and not related to Uralkali, who are reportedly seeking reimbursement themselves.
"When the contract was terminated, Haas had a salary arrears to me for 2022. And they still haven’t paid it," he told RBC.
"I’m only talking about the fact that contractual obligations were not fulfilled.
"You also need to understand that we had two independent contracts. And breaking the agreement with the title sponsor did not have a direct impact on my future in the team.
"So they [Haas] made two separate decisions. I didn't see my money, so we're going to court."