As part of his annual pledge to slowly give away his fortune, Warren Buffett has now donated around $3.6 billion of his shares in Berkshire Hathaway to a number of charities. Among the five charities that will be getting portions of the donation is the foundation that was started by his colleague, the Bill and Melinda Gates Foundation.

The massive donation will mark the 14th annual pledge for the billionaire investor. The donation comes in the form of around 16.81 million Class B shares of Buffett's company.

All in all, Buffett has donated more than $34.5 billion since he started his pledge back in 2006. The 88-year-old billionaire previously promised to donate a huge portion of his fortune each year to different charities. Last year, Buffett donated around $3.4 billion.

This year, Buffett's donation will be going to five charities. A major portion, or around four-fifths, of the amount will be going to the Gates Foundation. Meanwhile, the rest will be going foundations started by Buffett's family members.

This includes the foundation started in honor of Buffett's late first wife, the Susan Thompson Buffett Foundation, and the charity run by Buffett's children Susan, Peter, and Howard called the Howard G. Buffett Foundation, the Sherwood Foundation, and the Novo Foundation.

Buffett's Berkshire Hathaway shares will be sold off to finance the different charitable activities of each foundation. Buffett had previously expressed his desire to have his donations immediately spent once they are given. Apart from the foundations started by Gates and Buffet's family, the successful investor also donates to other organizations and charities outside of his annual pledge.   

Since 1965, Buffett has established Berkshire Hathaway into the biggest investment firm in the world.

The conglomerate is now worth more than $522 billion, owning several iconic businesses such as Dairy Queen, Geico Insurance, and BNSF Railroad. The company also owns major stakes in large companies including Apple and Wells Fargo.

Despite donating a large portion of his Berkshire Hathaway shares, Buffett still owns around 15.7 percent of the company he started. Buffett has so far given away over 45 percent of his holdings since 2006. The amount of money he has given away has done little to dent Buffett's overall fortune, which is estimated to still be around $87.5 billion.

Buffett's remaining wealth still places him as the world's fourth-richest person, right behind Bill Gates and Amazon founder Jeff Bezos. Bezos currently tops the list with a fortune worth around $157.8 billion prior to his divorce settlement. Despite losing some of his fortunes as part of his divorce settlement with his wife MacKenzie Bezos, the e-commerce founder still retained his rank as the world's richest person.