[5] In July 2019, the company acquired TRANZACT, a direct-to-consumer health care insurance marketplace specializing in Medicare Advantage plans, for $1.3 billion.

[7] On 9 March 2020, Aon announced its planned acquisition of Willis Towers Watson for nearly $30 billion in an all-stock deal that would have created the world’s largest insurance broker.

[15] It also acquired Aerosure, an aviation insurance specialist focused on the Australia, New Zealand, and the Pacific Island region.

[17][18] In July 2022, the company acquired Butterwire, a fintech provider of data analytics, artificial intelligence, and machine learning platforms.

[3][22] Towers Watson CEO John Haley was accused of having a conflict of interest since he was to receive $165 million from the completion of the deal.

Haley had disposed of 55% of his shares in the company for a $10 million profit in early March 2015 while the merger negotiations were ongoing and before the stock price dropped on the news of the acquisition.

[26] The defendants tried to collect $54 million from their directors and officers coverage, but were rejected by the courts as the policy had an exclusion for claims that would "bump-up" the price of an acquisition.