The billionaire on Monday donated about $3.17 billion of Berkshire Hathaway stock to the Bill & Melinda Gates Foundation as well as four other family charities, Reuters reports. This marks his 12th annual donation to the group of charities.

Buffett’s gift included 18.63 million Class B shares of his company’s stock, which carried a value of $170.25 each at the market’s close on Monday. Since taking control of Berkshire Hathaway in 1965, Buffett has given away more than 40% of his stake in the company, according to Reuters. But even with the new donation, he still owns about 17%.

In addition to the Gates Foundation, the others that received this round of funding are the Susan Thompson Buffett Foundation, which is named for the billionaire’s first wife, and his children’s foundations: the Howard G. Buffett Foundation, Sherwood Foundation and NoVo Foundation.

Bill Gates, a close friend of Buffett, will receive about $2.42 billion of Monday’s donations, according to Reuters. The Microsoft founder’s organization focuses on addressing issues such as global health, poverty and education, and the new gift from Buffett will likely be spent on those causes.

In 2006, Buffett pledged to eventually give away all his shares of Berkshire Hathaway, and along with Gates, has since convinced other billionaires to make similar commitments through their Giving Pledge campaign.