(Bloomberg) -- Wirecard AG’s shares have whipsawed this year after a series of reports alleging irregularities at the payment company’s Singapore unit. Wirecard has repeatedly denied wrongdoing, but investors remain jittery. The whole situation is so volatile that authorities halted short sales of the stock, and brokerage Keefe, Bruyette & Woods suspended its coverage of the company, saying it can’t come to an informed investment opinion given all the noise. Authorities from Singapore to Germany are investigating.

1. What is Wirecard and what does it do?

Wirecard is a developer of software and systems for online payments and fraud protection used across the internet. Its technology helps process smartphone payments, issue credit cards, and detect fraud. The firm’s revenue almost doubled to 2.1 billion euros ($2.4 billion) in the two years to 2018, following acquisitions of at least 18 other companies in an expansion masterminded by Chief Executive Officer Markus Braun. In September, Wirecard replaced Commerzbank AG in Germany’s 30-company DAX stock index alongside titans such as Volkswagen AG, Siemens AG, and Deutsche Bank AG.

2. What are the claims against Wirecard?

In a series of articles starting on Jan. 30, The Financial Times reported allegations of accounting fraud by employees at the company’s unit in Singapore. The stories cite a preliminary report from Singapore law firm Rajah & Tann, which Wirecard had hired to look into the allegations.

3. What is the company’s response?

Wirecard says the allegations are baseless, possibly brought forward to damage the company or profit from short-sales. CEO Braun said the findings from a deeper follow-up investigation by Rajah & Tann will be available in “a matter of weeks” and that he’s confident the new report will clear Wirecard and its employees of wrongdoing. An inquiry by an internal compliance team already concluded that many of the allegations are based on material that’s faulty or forged, the company said.

4. Hasn’t Wirecard always been controversial?

The company got its start as a provider of financial services to the gambling and adult entertainment industry, operating in murky waters. While Wirecard is now focused on more mainstream clients, its business model remains complex and it has had to defend its reputation repeatedly. The shares dropped -- but later more than recovered -- after past claims were published about accounting irregularities in 2008 and fraud allegations in 2016 that Wirecard denied. Those allegations led to a market manipulation conviction against a journalist in 2012, and a fine against one of the suspects behind the 2016 report.

5. What are the authorities doing?

German financial regulator BaFin on Feb. 18 banned short sales of Wirecard for two months, saying the affair poses a serious threat to market trust in Germany. The short-selling ban was coordinated with Munich prosecutors, who had already launched a probe into potential market manipulation in Wirecard shares. Prosecutors said they’re investigating a complaint filed by an investor against an FT journalist. Police in Singapore are also looking into the matter and searched Wirecard’s offices in the country on Feb. 8.

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