Twitter founder Evan Williams is now a billionaire (on paper)

SAN FRANCISCO -- Twitter just minted a billionaire -- at least on paper.

Evan Williams, the 41-year-old co-founder of Twitter, owns 12% of the social media company that is expected to go public next month, according to a filing with the Securities and Exchange Commission on Thursday.

Twitter has been valued on the secondary markets at about $9.4 billion, making Williams’ stake worth more than $1.1 billion.

Forbes is estimating Williams, Twitter’s largest individual shareholder, may be worth closer to $1.4 billion based on current valuations.

Fellow co-founder Jack Dorsey’s 4.9% stake is worth a cool half-billion.

Williams, the company’s former chief executive who is known to the nearly 1.7 million that follow him on Twitter as “@ev,� is no longer involved in the day-to-day operations of Twitter. He is working on a new project: an editorial website called Medium.

Notably missing from the filing: Co-founder Biz Stone. He has apparently sold enough stock not to be listed as a major shareholder.

ALSO:

Twitter drawing on lessons learned from Facebook IPO

Twitter IPO hurdle: The service is well known but not widely used

Twitter co-founders speak at all-hands company meeting ahead of IPO