Barcelona are suing former player Neymar for 8.5m euros (£7.8m) for breach of contract over his world record move to Paris St-Germain.
The Brazil international made the 222m euro (£200m) move to the French club in August after buying out his contract.
Barcelona now want him to return a renewal bonus he was paid when he signed a new five-year deal just nine months before forcing through the move.
"The club demands the player return the already paid sum as he has not completed his contract," it said.
As well as the 8.5m euro bonus, the club wants "an additional 10% because of delayed payment".
The statement continued: "The club also requests Paris St-Germain take on responsibility for the payment of these fees if the player cannot do so himself."
Paris St-Germain later responded to say they were "surprised" by Barcelona's statement, adding: "The club repeats that, along with Neymar Jr, it strictly respected all applicable laws and rules and can only regret, once again, the attitude of FC Barcelona."
The lawsuit was submitted on 11 August to the Labour Tribunal in Barcelona, eight days after Neymar's stunning move to Ligue 1.
Following the transfer, Barcelona announced the club was withholding a further 26m euro (£23m) loyalty bonus from the player.
Moreover, Barca urged PSG to pay the amount they are seeking if Neymar – who is reported to earn 30 million euros a year after tax for the next five years in Paris – isn't able to meet their demands.