Jack Dorsey, the CEO of both Twitter and digital payments platform Square, said on Tuesday that he will donate $1 billion worth of equity in Square to his Start Small LLC to fund COVID-19 relief around the world. Dorsey made the announcement in a tweet, revealing that the sum equates to roughly 28 percent of his current net worth, or about $3.6 billion. The announcement marks the most significant philanthropic effort from the 43-year-old tech executive in his career.

Dorsey is far from as wealthy as tech moguls like Facebook CEO Mark Zuckerberg, Microsoft co-founder Bill Gates, and Amazon CEO Jeff Bezos. Yet, thanks to the performance of the shares he owns in both Square and Twitter, he is still a billionaire and until last year had not openly made plans to donate a majority of his wealth beyond the existence of the Start Small fund, which Forbes reports is a donor-advised fund that doesn’t have to disclose where its investments are directed.

I’m moving $1B of my Square equity (~28% of my wealth) to #startsmall LLC to fund global COVID-19 relief. After we disarm this pandemic, the focus will shift to girl’s health and education, and UBI. It will operate transparently, all flows tracked here: https://t.co/hVkUczDQmz — jack (@jack) April 7, 2020

Dorsey appears to want to change that. He says the $1 billion going into Start Small today will be publicly tracked, and he even tweeted the public Google Sheets spreadsheet that will track the spending. It includes an existing $100,000 donation Dorsey gave to America's Food Fund. He says following the COVID-19 relief effort, Start Small will shift focus to “girl’s health and education, and UBI,” or universal basic income.

Dorsey says UBI and women’s health and education “represent the best long-term solutions to the existential problems facing the world,” and UBI requires funding for experiments to test its efficacy in the real world. He also offered some clarity on why he decided to use Square shares — “I own a lot more Square,” he says — and explained why Start Small is structured as an LLC instead of using a more traditional philanthropic structure like a 501(c)(3) nonprofit, as the Bill and Melinda Gates Foundation is structured.

Why pull just from Square and not Twitter? Simply: I own a lot more Square. And I’ll need to pace the sales over some time. The impact this money will have should benefit both companies over the long-term because it’s helping the people we want to serve. — jack (@jack) April 7, 2020

“Why now? The needs are increasingly urgent, and I want to see the impact in my lifetime,” Dorsey tweeted in the final message of his thread. “I hope this inspires others to do something similar. Life is too short, so let’s do everything we can today to help people now.”