Twitter tweeted that the company had filed its S-1 registration documents with the SEC, the first public step toward an IPO. Twitter's filing is somewhat unique in that it is confidential. Under the JOBS Act, an "emerging growth company" can file a confidential S-1 if revenues are less than $1 billion. The S-1 does not have to be released publicly until 21 days prior to the IPO. Private sales of Twitter stock lead to a valuation of about $10 billion on the company.