The ultimate group discount? Or a case of  “pop” as the sound of the group buying mania evaporates in a cloud of, well, discounts thanks to accounting reality hitting the already tottering market leading Groupon of the US?

Reports over the weekend said Groupon had changed the way it presents its revenue, slashing its top-line sales figure by more than half ahead of a float that’s already been delayed by three months or more. Instead of Groupon counting as revenue the full dollar amount of its coupons, it will now count only the commission the company gets above the coupon price. (That’s commission it receives on the amount remaining after the discount, say 50%).

In a filing with the US Securities and Exchange Commission on Friday Groupon cut its 2010 sales from $US713 million to $US313 million after deducting the fees paid by merchants.

It also adjusted first-half 2011 reported sales downwards from $US1.52 billion to $US688 million. Groupon said the previous documents filed with the Securities and Exchange Commission had “an error in presentation”. (That’s like saying the “dog ate my homework”). Errors in presentation should have been easy to fix up once you had checked the presentation itself, you’d have thought?

“The Consolidated Financial Statements have been restated for the presentation of revenue on a net basis for all periods presented. See Note 2 to our Consolidated Financial Statements. In addition, the six month period ended June 30, 2011 has been restated to reduce selling, general and administrative expense to correct for an error. See Note 2 to our Condensed Consolidated Financial Statements,” the SEC filing said.

And Note 2 read:  “The Company has restated its previously issued Consolidated Statements of Operations for the years ended December 31, 2008, 2009 and 2010 to correct for an error in its presentation of revenue. Most significantly, the Company restated its reporting of revenues from Groupons to be net of the amounts related to merchant fees. Historically, the Company has reported the gross amounts billed to its subscribers as revenue.”

In other words, the Groupon accounts have been tidied up and regularised accounting to more conventional accounting. But no profits, of course.

So, for instance, the company is now reporting revenue of $US392.6 million for the second quarter of this year, on gross billings of $US909.2 million. Previously, it claimed $US878 million.

The restatement, which could delay its plans for an IPO, came on the same day that the company lost its number-two executive, a bad look for a company still looking to float and allow insiders to cash in.

Margo Georgiadis, chief operating officer, has left after just five months at Groupon. In something of an indictment of Group, she has returned to where she came from, Google, the company which offered $US6.4 billion for Groupon, but was rebuffed.

Georgiadis returned to a job as head of Google Americas. According to various media reports, she wrote in a departing note that she had “complete confidence in the team’s ability to realise its mission”, she left the Chicago-based company to return to Google as president of the Americas region. Georgiadis had struggled in dealings with Andrew Mason, Groupon’s young chief executive, she told associates, according to reports in The Financial Times and other papers on the weekend.

“She was brought in to implement strategy and operational discipline and she did it, but Andrew was fighting her every step of the way,” one colleague told the Financial Times. This person described the former McKinsey consultant as effective but corporate in outlook, while Mr Mason made decisions more instinctively.

The next issue to watch for with Groupon is slowing revenue growth. There are already reports (anecdotal) that the company and its competitors are facing slower growth in transactions, which are generating less revenue because of bigger revenue shares being paid to selected retailers and merchants who generate good sales.

And the news of the restatement and possible delay to the float of Groupon in the US (nothing could be sold in the present febrile climate in the sharemarket) is bad news for the Australian wannabes, such as James Packer, who with a group of investors, has bought a stake in local coupon sites, and Catch of the Day. The group invested $80 million in the two websites. Media reports in May said the buyers including James Packer’s Consolidated Press Holdings, Seek co-founder Andrew Bassat and American hedge fund Tiger Global. The investment valued the group at $200 million.

There’s been talk that Nine Entertainment is looking to sell its stake in its Cudo coupon site for around $30 million, if partner Microsoft sells.

If Groupon can’t get its IPO away, investors belief in the coupon industry will fade, especially if there are any more accounting restatements. Friday’s was the third so far this year. Certainly floats and sales of Australian sites won’t happen for months and months given the market volatility at the moment.