Image source: Groupon.

Groupon (NASDAQ:GRPN) shares are plunging in after-hours trading, following the release of the online deal provider's fourth-quarter results.

In the holiday quarter, Groupon saw sales jump 20% year over year to land at $768 million. Non-generally accepted accounting principles earnings stopped at $0.04 per share, up from $0.03 per share a year ago. Analysts were looking for about $0.02 of earnings per share on $718 million in sales.

So the company easily exceeded expectations in the fourth quarter, boosted by strong consumer engagement with Groupon deals over the holiday season. But shares are down 10.3% at press time, because the forward guidance was far less rosy.

In the first quarter, Groupon expects a pair of recent acquisitions to add $50  million to revenue while hampering EBITDA profit by $20 million. Given these puts and takes, revenue guidance for the upcoming period centers around $735 million while the earnings estimate ranges from a $0.02 loss per share to a $0.06 profit per share.

"Our mobile business continued to gain momentum as our worldwide mobile transaction mix increased more than 10% in the quarter, to nearly 50% in December," Groupon CEO Eric Lefkofsky said in a prepared statement. "With another 9 million downloads this quarter, we now have nearly 70 million app downloads to date."

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