Sixteen years ago, the now-91-year-old investor promised in a pledge letter to gift 99% of his wealth to philanthropy by the end of his life. He hit the halfway mark of that goal in 2021.

Much of Buffett’s remaining wealth, estimated at $117 billion in 2022, is already spoken for. Since 2006, he has given away shares through annual gifts to five foundations, the most prominent of which is the Gates Foundation. 

But the charitable organization that Buffett helped formed himself in 1964—the Susan Thompson Buffett Foundation, a major funder of abortion rights—is preparing to receive up to $100 billion. The organization has been hiring staff and making plans on how to spend additional money from Buffett, the Wall Street Journal reported. 

Here’s what is currently known about Buffett’s estate planning, and the Susan Thompson Buffett Foundation. The Journal’s recent report on which foundations could expect his undistributed shares, and the amount they might receive, prompted Buffett to say it contained “a significant number of inaccuracies,” without clarifying further. 

Neither Buffett nor The Susan Thompson Buffett Foundation responded to inquiries from Fortune about confirming the potential windfall for the charity. The Gates Foundation told Fortune it had nothing to add beyond the statement Buffett gave to the Journal.

Warren Buffett’s charity plans

In 2006, Buffett told Fortune he would start giving away his money, and that 85% of his Berkshire Hathaway stock would eventually go toward five foundations. He planned to give more than 80% of the shares to the Gates Foundation, which was the world’s largest philanthropic organization at the time. Buffett was also close friends with the Gates family.   

Buffett said he would earmark 10 million B shares from Berkshire Hathaway for the Gates Foundation, 1 million B shares for the Susan Thompson Buffett Foundation, and 350,000 B shares for three foundations headed by each of his children, according to letters to the charities. The pledges to those five foundations accounted for 85% of Buffett’s stock in 2006.

Then in 2012, Buffett decided to give an additional $3 billion in Berkshire Hathaway shares to the foundations run by his children, meaning that about 90% of his stock was earmarked for specific charities. 

The question of what will happen to the remainder of Buffett’s shares has garnered great interest. Gates Foundation staff reportedly anticipate a “flood of funding” in what they refer to as Project Lincoln, the Journal reported. 

But the Susan Thompson Buffett Foundation is also preparing to receive up to $100 billion in undistributed shares, sources told the Journal. 

It is unclear what changes have been made to other designated charities that would make this possible.

What is the Susan Thompson Buffett Foundation? 

Buffett established the foundation with his late wife Susan “Susie” Thompson Buffett in 1964. It was known as the Buffett Foundation for 40 years; he renamed it in his wife’s honor after she died in 2004. Upon Susan’s death, nearly all of her estate, valued at close to $3 billion in 2004, went to the foundation. 

“She and I established the Susan Thompson Buffett Foundation to focus intensely on important societal problems that had very limited funding constituencies,” Buffett wrote to the foundation’s directors in his 2006 pledge, adding that he hoped the foundation “maintains its strong focus on just one or two important issues.” 

The foundation does not publicize its focus, but many outlets have reported that much of its work centers on pro-choice advocacy and reproductive policy. It donated more than $1.5 billion to abortion causes between 2001 and 2014, per a Mother Jones investigation. Among those recipients are Planned Parenthood, the National Abortion Federation, and the Guttmacher Institute, according to Mother Jones. 

In 2013, STBS ranked third among the foundations that paid out the most grants, Bloomberg reported, crediting it for becoming “by far the most influential supporter of research on IUDs and expanding access to the contraceptive.” In 2020, it paid out $647 million to charitable causes, according to the foundation’s tax filings compiled by ProPublica. 

Yet the foundation has conducted most of its work out of the spotlight. Its website is inconspicuous and speaks about offering scholarships for Nebraska college students. STBS’s former director for domestic programs, Judith DeSarno, said in a 2008 interview with Bloomberg that she would instruct reproductive health groups who received its grants, “You can’t send out a press release, and you can’t talk about, ‘We got Buffett money.’”