Xero became a $5 billion company in morning trade on Thursday, as shares jumped as much as a further $2.20, rising to $39.50 and valuing the accounting software company at $5.04 billion.
As recently as early September, the shares were trading for as little as $17.60.
Xero shares had already jumped more than 12.5% on Wednesday, with the market effectively deciding the company was worth $529.2 million more than the day before.
Last month, Xero said it expects to report sales of just over $30 million for the six months to September.
That figure is up 84% from its $16.5 million in sales it made in the same six months last year.
In mid-October, Xero raised $180 million from investors, including American tech investor and billionaire venture capitalist Peter Thiel.
Speaking from the United States, Xero chief executive Rod Drury told Radio New Zealand's Morning Report programme the market is not expecting the seven-year-old company to post a profit any time soon.
"What they want us to do is to take that money we've invested and continue to build a great team and even increase our investment in software developers ... so it's quite different for most New Zealand-based businesses but it's very common with other businesses up here in the US.
Technology commentator Peter Griffin says when Xero chief executive Rod Drury set out his vision for the firm many years ago he said accounting software is key for any business to get an understanding of its operation.
Mr Griffin says Xero provides a very good product which has successfully put things like payroll, invoicing, expense claims, management reporting and accounting feeds into the accounting package.
He says the questions now are whether Xero can succeed in the United States and can it do it quickly enough to keep the shareholders happy.
Mr Griffin says Xero's major US competitor is Intuit which has $4 billion a year in revenue and 8500 employees.
He says the big question is whether Xero can maintain its momentum in the US market and take market share away from Intuit - and that will decide whether the type of growth Xero has experienced in the last couple of weeks is sustainable.