It's also been no secret that Bezos has been gradually selling off $1 billion worth of Amazon stock per year, potentially to put towards ventures such as a spaceship project.
Bezos owns almost 80-million shares of Amazon stock, earning him $2.4 billion on Friday alone.
Gates is believed to be the only other person to reach $100 billion in 1999.
Jeff Bezos arrives for the third day of the annual Allen & Company Sun Valley Conference, July 13, 2017 in Sun Valley, Idaho. Amazon shares hit a record on Black Friday - one of the year's busiest shopping days - joining a broader stock market rally.
Bezos, who surpassed Gates as the world's richest man in October, suggested he knew he needed to up his philanthropy earlier this year when he took to Twitter to ask for ideas. He had given away around $500m of Amazon shares since 2002, according to analysis of Form 4 filings, while Gates gifted $4.6bn in a single donation back in August to an unknown benefactor.
The hike in Mr Bezos's wealth had soared by $32.6bn this year up until Thursday, with the extra $2.4bn landing in his pocket ahead of the consumer frenzy, and secures his position as the world's richest man.
All eyes are now on Bezos to see what he decides to do with his fortune.
Mr Gates is now second in the Index with $89,1bn, followed by Warren Buffet ($78.7bn) and Spain's Armancio Ortega ($75.9bn).
He wrote: "I'm thinking I want much of my philanthropic activity to be helping people in the here and now - short term - at the intersection of urgent need and lasting impact".