Neptune Insurance Holdings (NP.US), a U.S. excess and surplus (E&S) flood insurance underwriting and distribution service provider, announced the terms for its initial public offering (IPO) on Monday. The St. Petersburg, Florida-based company plans to raise $350 million by offering 18.4 million shares at a price range of $18 to $20 per share, with the entire offering consisting of secondary market stock transfers (no new shares issued).

Cornerstone investors T. Rowe Price and Alliance Bernstein have committed to purchasing $75 million worth of shares, representing 21% of the offering size. Based on the midpoint of the price range, Neptune Insurance Holdings would achieve a fully diluted market capitalization of $2.8 billion.

Neptune Insurance Holdings operates as a data-driven managing general agent (MGA) specializing in flood risk mitigation solutions for individual homeowners and businesses. The company distributes various residential and commercial insurance products through its nationwide agent network, including primary flood insurance, excess flood insurance, and parametric earthquake insurance.

Notably, Neptune Insurance Holdings does not assume any balance sheet insurance risk nor handle claims processing for the policies it sells. Its core business model centers on providing underwriting and policy management services on behalf of insurance and reinsurance companies through its proprietary Triton underwriting platform and Poseidon policy management platform.

Founded in 2017, Neptune Insurance Holdings generated revenue of $137 million in the 12 months ending June 30, 2025. The company plans to list on the New York Stock Exchange under the ticker symbol "NP".

The IPO's joint bookrunners include Morgan Stanley, JPMorgan Chase, Bank of America Securities, BMO Capital Markets, Goldman Sachs, Evercore ISI, Deutsche Bank, Keefe Bruyette Woods, Mizuho Securities, Piper Sandler, Raymond James, and TD Securities. The final offering price is expected to be determined during the week of September 29, 2025.