What was expected to be one of the hottest stock offerings of the year fell into deeper turmoil Friday, as daily deals pioneer Groupon Inc. said it was cutting its reported revenue in half, and its No. 2 executive left the company.

Regulators have been scrutinizing Groupon's accounting since it filed for an initial public offering that could value the Chicago company at $20 billion.

Groupon's Restatement Read the Filing

On Friday, Groupon said it would change what it books as revenue after discussions with the Securities and Exchange Commission. It will now only count as revenue its commission on sales, rather than the total value of an online coupon. Previously, when it sold a restaurant gift certificate for $10, for instance, it would book the full amount, even though a portion went to the business owner.

That change reduces Groupon's stated revenue for 2010 to $312.9 million, down from the $713.4 million previously reported.

The company argued in its amended filing document that it had always told investors to measure its value based on the cash it collected minus merchant payments.

Also Friday, Groupon said its chief operating officer, Margo Georgiadis, is returning to Google Inc. as a senior executive, just five months after she was hired away.

The Groupon logo is engraved in a glass office partition in the company's Chicago headquarters. Scott Olson/Getty Images

Groupon founder and Chief Executive Andrew Mason said Friday in a blog post that Groupon has hired many senior executives this year, but not all have worked out. He didn't elaborate.

A call to Ms. Georgiadis wasn't immediately returned. In a statement on the company's blog, Ms. Georgiadis said that Groupon "is on a terrific path," and said she has "complete confidence in the team's ability to realize its mission." Prior to joining Groupon, Ms. Georgiadis served as Google's vice president of global sales operations.

One person familiar with the situation said Ms. Georgiadis didn't fit in at Groupon. Mr. Mason would often go around her to other executives, a move that frustrated Ms. Georgiadis, added the person.

Ms. Georgiadis's departure comes amid an IPO that has brought intense speculation from investors over the viability of Groupon's business model.

The company canceled a road show it had scheduled for early September and pulled back on plans to go public. It is still evaluating its options on a week-by-week basis.

This is the second operating chief to leave Groupon this year. Rob Solomon, a Silicon Valley veteran who joined Groupon in early 2010, said he left the company because it got too big.

The company hasn't hired a recruiting firm to look for a replacement for Ms. Georgiadis, said a person familiar with the matter. That decision could change upon further consultation with the board, added the person.

Instead, Mr. Mason said Ms. Georgiadis's departure is an opportunity to "reorganize in a way that reflects our evolving strategic priorities." He said sales, channels, international and marketing will now report to him.

—John Letzing contributed to this article.

Corrections & Amplifications

The last name of Groupon's chief operating officer, Margo Georgiadis, who is returning to Google, was misspelled Giorgiadis and Geordiadis in subsequent references in an earlier version of this article.