Longfin Corp. took advantage of post-financial-crisis rules designed to create jobs and help young companies go public. But the financial-technology company, which was valued at $5.4 billion as recently as 10 days ago, is now under investigation by the Securities and Exchange Commission after it failed to disclose important information and left a trail of misstatements behind.
Since Longfin’s December initial public offering, which raised $5.7 million, the company’s price first rose 13-fold, then fell by 80%, all in less...