Telecommunications enabler Twilio has raised a $100 million series E round that values the company at over $1 billion, according to government filings.

The news was first reported in Forbes, citing research firm VC Experts, which uncovered a Delaware filing revealing the large round. With 8.8 million series E shares authorized, that means the company has raised - or is about to raise - a few pennies short of $100 million.

According to the Forbes report, this more than doubles Twilio's total capital raised: It had previously raised $103 million in four rounds, the most recent of which was a $70 million series D in June, 2013. The lead investors in that round were Bessemer Venture Partners, Draper Fisher Jurvetson, and Redpoint Ventures. The most recent round also reportedly doubles the company's valuation, from $500 million, putting it in the 'unicorn club' (a term for venture-backed companies worth more than $1 billion).

Twilio has built a suite of services used by developers to integrate telephone capabilities into their apps, from placing a call to sending text messages. As part of that suite of services, it operates an extensive telephony network of its own, in order to connect its customers' apps to telephone networks all over the world. It added video calling services to that suite in March.