Square has authorised a private offer of one million shares at $135 each, which values the privately-held company at $5 billion, according to Bloomberg.

Rizvi Traverse Management and a number of other investors are interesting in buying the stock from employees and other early shareholders, according to people familiar with the matter.

Square’s shares are not publicly traded although there is ongoing speculation about an IPO.

The company was valued at $3.25 billion in August 2012, indicating a more than 50-per-cent surge over the past 18 months.

Techcrunch points out that Square’s valuation has grown in step with the total amount of payments it processes. From an annualised figure of $1.46 billion in June 2011, the amount processed by Square has grown to $20 billion for 2013. It is predicted to process $30 billion this year.