Groupon, the discount deals website that snubbed a $6bn (£3.9bn) offer from Google, is to raise $1bn of its own.

The company emails its 35 million subscribers with targeted daily deals from local businesses and is by some measures the fastest-growing internet firm ever. In two years the company has sold 18m coupons in the US, expanded to 35 countries and has 3,000 staff, mostly in sales.

According to a regulatory filing, Groupon is seeking to issue 30.1m preferred shares of stock at $31.59 a share – about $950m. The private share issue would value the two-year-old firm at up to $7.8bn, according to VC Experts, the financial website that first reported the move.

Earlier this month, Groupon rejected a buyout offer from Google reported to be worth about $6bn. Andrew Mason, founder and chief executive, is believed to be studying the possibility of floating the company on the stock market. Mason confirmed via Twitter that the company was looking for new funds. "Groupon is in the process of completing a new round of financing – we'll let everyone know when there's more to announce," he wrote.

Groupon has been aggressively beefing up its business in recent months. The company recently bought a local marketing company, Ludic Labs, and has begun expanding around the world. Groupon operates in Britain and recently bought rivals in Hong Kong, Singapore and Taiwan. The company has also recruited Jason Child, Amazon's vice-president of finance, as its chief financial officer.

If Groupon raises $950m, it would be the largest equity financing since Pixar sought about $500m in 1995. Backers include the venture capital firms Accel Partners and New Enterprise Associates, Chicago-based investors Eric Lefkofsky and Brad Keywell and the Russian firm Mail.ru Group, a Facebook backer formerly named Digital Sky Technologies.

The firm makes its money by taking a 50% cut of each discount coupon soldon its website.