Investment firm Blackstone is buying Aon's technology-enabled benefits and human resources assets in a deal valued at up to $4.8 billion.
The transaction includes $4.3 billion at closing and the potential for up to an additional $500 million based on future performance.
The companies said Friday that the Aon assets being purchased are the largest benefits administration platform in the U.S., serving approximately 15 percent of the U.S. working population across more than 1,400 companies.
The deal is targeted to close by the end of the second quarter.
Aon Plc., based in London, topped profit expectations as well for the fourth quarter Friday, with net income of $502 million.