British insurance broker Aon Plc has accused the founder of Brazilian health and benefits insurance broker Admix of defrauding it when it acquired the company four years ago in a 1.35 billion reais ($300 million) deal, according to arbitration and court documents reviewed by Reuters.

The sale contract with Admix founder Cesar Antunes da Silva included a clause calling for Aon to pay him up to 150 million reais two years after the deal closure if certain revenue targets were met. Another 80 million reais were placed in an escrow account as guarantee for any problem in the deal, a common practice in M&A transactions.

Citing what it called “fraud and omissions” by da Silva in the sale process, Aon in 2018 did not pay the earn-out clauses or release the amount in the escrow account, according to the documents. Aon is seeking at least 200 million reais in damages via arbitration.

Lawyers for da Silva said Aon was trying to use the arbitration to compensate for losses stemming from its own “mismanagement” of Admix after the acquisition, according to the documents.

They said the insurer took two years to complain of omissions and are demanding that Aon pay the remaining value in the escrow account and the earn-out payments.

Aon and da Silva’s lawyers declined to comment for this story, saying the arbitration was confidential.

The arbitration, which began in December 2018 in Sao Paulo, is registered by the International Chamber of Commerce under the number 24146/GSS and details of its contents have not been previously reported.

The dispute underlines how disappointing the deal has proven for Aon, which is aiming to become the world’s largest insurance broker. When it was announced, the then head of Aon’s health and benefits division, John Zern, said the acquisition doubled the brokerage giant’s presence in Brazil, while its head for Risk Solutions in Latin America, Fernando Pereira, said the deal would enhance Aon’s activities in Latin America. Both have left the company since the deal.

At the time, Admix had 1.4 million beneficiaries across 6,700 companies of all industries and sizes and placed 2 billion reais in health and benefits premiums a year.

Aon has also asked the arbitration judges to revalue Admix, alleging irregular underwriting policies, and to reimburse the price difference.

The alleged underwriting irregularities happened only after the company was sold, da Silva’s lawyers say, according to the documents.

Aon also alleges Admix failed to inform it about contract cancellations, including the cancellation of a high number of contracts before the deal closed by health care operator Unimed. Da Silva argued in his response in the arbitration that most of those were transferred to other insurance brokers within the same group.

Aon also accused the Admix founder of failing to disclose significant labor lawsuits filed by its own employees.

Aon’s arbitration lawyers also accused a former Admix insurance broker of intimidating witnesses because he sued certain of the British insurer’s employees who had made depositions within the arbitration proceedings and accused him of fraud. The broker, Nadjair Diniz Barbosa, and his lawyer declined to comment.

Aon did not disclose the arbitration in its 2019 financial statements as it has done with other arbitration proceedings in New Zealand and the United States, and antitrust investigations in Europe. Aon declined to comment on why the arbitration was not disclosed in the financial statements.

Aon announced on Monday a $30 billion deal to acquire rival Willis Towers Watson and become the world’s largest insurance broker. ($1 = 4.5059 reais) (Reporting by Tatiana Bautzer; Editing by Christian Plumb and Rosalba O’Brien)