Lagarde made no comment to reporters as she went into the Court of Justice of the Republic, a special court that handles ministerial misconduct cases.
Tapie was awarded 400 million euros by arbitrators after he claimed that he had been defrauded in the sale of sportswear group Adidas to the Crédit Lyonnais bank, which was partly state-owned at the time.
Magistrates are looking into accusations that the arbitration was fixed by the Sarokzy government in return for Tapie’s support during the preceding presidential election.
They want to know why Lagarde, as finance minister, chose to go to arbitration rather than to court.
The IMF chief has escaped criminal charges, which would have obliged her to follow her predecessor Dominique Strauss-Kahn’s example and resign, although she has been placed under a special witness status that means she could be charged later.
Five other people have been charged.
One of them is here former chief of staff, Stéphane Richard, now head of the Orange telecoms company.
He has not hidden his annoyance at receiving harsher treatment than the minister he served and seems to contradict Lagarde as to whether she was personally responsible for a letter relating to the case written in October 2007.