Aon Plc is aiming to raise approximately $13.5 billion through a high-grade bond offering to help finance its planned $17 billion acquisition of USI Insurance Services. The transaction represents one of the largest merger and acquisition financing deals anticipated in 2026.

The size of the bond offering could fluctuate depending on investor demand, which is reported to have reached around $17 billion following recent marketing efforts. Aon is currently offering notes in seven tranches with maturities spanning from three to 30 years. Initial pricing talks for the longest-dated notes suggest a yield about 1.5 percentage points over comparable U.S. Treasuries. Except for the 30-year notes, all bonds would carry provisions requiring redemption at 101 cents on the dollar plus accrued interest if the acquisition is not completed by December 1, 2027.

The offering is being managed by Bank of America Corp, Citigroup Inc, HSBC Holdings Plc, Morgan Stanley, and Wells Fargo & Co. Aon reached an agreement last month to acquire USI Insurance from private equity firm KKR and other shareholders in an all-cash deal financed with debt. The acquisition is expected to close by the end of the year.

The purchase is intended to enhance Aon’s market presence, particularly among mid-sized corporate clients. Aon is recognized as one of the world’s largest insurance brokers, while USI Insurance Services provides brokerage and consulting services to both business and individual clients.

This bond sale is unfolding amid an increasingly challenging market environment. Borrowing costs rose further on Monday as credit and equity markets grappled with the impact of a high-profile call by leading artificial intelligence firms to slow the pace of AI development. Additionally, rising oil prices have exacerbated inflation concerns ahead of the U.S. Federal Reserve’s imminent interest rate decision.

The tougher financing conditions have led at least five companies considering high-grade bond offerings to postpone their plans in anticipation of more favorable market conditions. Despite this uncertainty, Aon is proceeding with its sizable bond offering to secure funding for the USI acquisition.