A startup that didn't get any funding in its first 7 years just raised $108 million - and is now worth over $1 billion

When business software company Apttus first launched in 2006, its three cofounders committed to do something that's rarely seen in tech startups these days: to build a company without raising any venture capital for as long as possible.

They believed the longer they waited, they could raise more later without giving up too much control to investors.

For the next seven years, Apttus didn't need any venture funding - it generated enough cash while remaining largely profitable, all while doubling in size every year. Its software, which helps companies generate quotes and handle contract work to close deals, quickly became a big hit, signing up its first $1 million deal less than 6 months after its founding, with just its sixth customer.

But as the company grew and the market opportunity became clear - Gartner sizes the Quote-to-Cash market Apttus is in at $31 billion - Apttus saw the need to invest more aggressively in sales and marketing to grab a larger market share. So in 2013, it had its first VC financing round worth $37 million, and earlier this year raised another $41 million (which was Salesforce's largest private investment at the time).

And just seven months after its last round, Apttus announced on Tuesday that it's raising yet again, a $108 million Series C round led by KIA and joined by Iconiq Capital, K1 Capital, and Salesforce Ventures - which the company says gives it a valuation of "significantly more than $1 billion."

"We were just looking at this market, and realized if we don't take it, somebody else will," Apttus CEO Kirk Krappe told Business Insider.

Krappe says Apttus is forecast to hit a revenue run rate of $120 million by the end of this year, while growing 80% annually. It currently has about 350 customers, including GE, HP, Salesforce, and PayPal, and is expected to have 1,400 employees by this year, quadruple 2013's headcount. Krappe also claims that Apttus' average deal size is bigger than some of the top cloud software companies, like Workday and NetSuite.

So why is Apttus so popular? Krappe says it's simply the fact that Apttus makes the entire sales process faster and easier. Once a salesperson gets in touch with a potential customer, Apttus helps put together the right product offering and financial terms of the contract, while also allowing legal paperwork to be taken care of within its software.

For example, GE has hundreds of thousands of different product options, and it could take a long time to manually come up with the right quote and contract terms for a potential customer - and it only gets more complicated in different regions and industries.

"We basically handle all the business process between the CRM system and the financial system. That's all very complicated stuff," Krapp said.

With the type of growth it's seeing, Apttus doesn't seem too far off from going public soon. Krappe acknowledges that Apttus' financial numbers are "IPO-ready," and that this round will probably be its last round before an IPO. But because Apttus didn't raise VC money until two years ago, he says the company's under no pressure from investors to have a liquidity event yet.

"We could IPO next year, but the key is what's the right thing for the company," he said.