Square files for IPO, says a single client cost it $5.7 million due to fraud

Square's new EMV reader.

On Wednesday, mobile payments processing company Square filed for an initial public offering (IPO), although it kept how much money it plans to raise and how many shares it plans to offer confidential.

The filing, however, offers an inside look at the financials of the increasingly popular point-of-sale (POS) company, which has gained a foothold in a traditionally slow-moving market by making customers out of coffee shops and boutique stores that might normally only accept cash.

Under the “Risk Factors” section of the form that Square is required to fill out for the Securities and Exchange Commission (SEC), the company noted a number of concerns that potential investors might have, but one risk factor that stuck out involved how Square addresses fraud.