Discount coupon website Groupon Inc. is preparing to go public with an estimates company value of at least $15-billion, according to DealBook.

Groupon has already turned down a $6-billion takeover bid from Google Inc. (Nasdaq: GOOG), More importantly, the start-up recently received a record $950-million in financing which it sad would be used to fuel global expansion, invest in technology, and provide liquidity for employees and early investors.”

Based in Chicago, Groupon was introduced in November 2008 and has since expanded into 35 countries comprising 50-million global subscribers.