(Reuters) - Hedge fund manager Bill Ackman kicked off fundraising for a new U.S.-listed closed-end fund on Tuesday, an effort people familiar with the matter say could bring in as much as $20 billion, more than double his assets under management, some of that from retail investors.

Last month, Ackman sold 10% of his firm, Pershing Square Capital Management, which has posted mostly strong double digit returns since 2019 after a spell of losses.

The new fund, Pershing Square USA Ltd, will offer lower fees for investors and quicker access to capital than traditional hedge funds, regulatory filings show. There will be no management fee charged for the first year after the fund's initial public offering and no performance fees ever.

It will be listed on the New York Stock Exchange and be available to anyone who can invest in the U.S., including pension funds, endowments and retail investors. Roughly 80% is expected to be raised by institutions, with retail investors making up the rest, a filing made Tuesday shows.

Ackman, a heavy user of social media platform X, referenced the fundraising on Tuesday when he messaged his 1.3 million followers "I am going to be busy for the next few weeks. $PSUS!!"

Investors, including ones unable to write the multimillion-dollar checks Wall Street hedge funds traditionally demand, can pay $50 a share for the new vehicle. At the end of June, Pershing Square Capital Management oversaw $18.7 billion in assets, according to a company document. This includes some $15 billion in assets in Pershing Square Holdings, the 10-year old closed-end fund listed in Amsterdam and London.

Ackman built his reputation as an activist investor with noisy campaigns at companies ranging from railway Canadian Pacific to payroll and tax services company ADP. He owned stakes in Chipotle Mexican Grill, Hilton Worldwide Holdings and Restaurant Brands International at the end of the first quarter.

Citigroup, UBS Investment Bank, BofA Securities and Jefferies are global coordinators and bookrunners for the initial public offering.

Ackman's recent string of strong returns -- Pershing Square Holdings earned 27% last year, 27% in 2021, 70% in 2020 and 58% in 2019 (It dropped 8.8% in 2022 when the market tumbled) -- follow a reorganization of the firm.

Taking the advice he usually gives to companies to perform better personally, Ackman re-engineered the way he invests and reversed double-digit losses in 2015 and 2016 followed by smaller declines in 2017 and 2018.