NEW YORK ( TheStreet) -- Shares of Groupon ( GRPN) fell sharply in late trades on Friday after the online deals company said it's revising previously reported fourth-quarter results to reflect an increase in its refund reserve and higher operating expenses. The company, which went public in early November at $20 and closed Friday's regular session at $18.38, said the changes would reduce its fourth-quarter revenue total by $14.3 million, its operating income by $30 million, its net income by $22.6 million, and its earnings per share by 4 cents. Groupon originally revenue of $506.5 million in the period. Groupon stated the revisions are "primarily related to an increase to the Company's refund reserve accrual to reflect a shift in the Company's fourth quarter deal mix and higher price point offers, which have higher refund rates. The revisions have an impact on both revenue and cost of revenue." In addition, the company said its Form 10-K would include an acknowledgement of "material weaknesses" in its internal controls as per the findings of its independent auditor Ernst & Young LLP. It apparently plans to hire another unnamed accounting firm though. "The Company has been working for several months with another global accounting firm in preparation for reporting on the effectiveness of its internal controls by the end of 2012, as required following Groupon's initial public offering last year," Groupon said in Friday's press release. "The Company continues to implement process improvement initiatives and augment its staffing, and is expanding the accounting firm's engagement scope to address the underlying causes of the material weakness." The stock was last quoted at $17.10, down 7%, on volume of nearly 900,000, according to Nasdaq.com. On the bright side, Groupon did affirm its outlook for income from operations of $15 million to $35 million in its fiscal first quarter on revenue of $510 million to $550 million. Wall Street is currently looking for revenue of $533.8 million in quarter. The sell side is fairly bearish on Groupon with 14 of 22 analysts covering the stock at hold (11), underperform (1), and sell (2). Check out TheStreet's quote page for Groupon for year-to-date share performance, analyst ratings, earnings estimates and much more.