US mobile payments provider Square now has more than one million merchants using its service, according to the company via Twitter. This figure is an increase from the 800,000 merchants who had signed up to Square’s service two months ago. The company is talking up its achievement in terms of US penetration: Co-founder Jack Dorsey pointed out that there are only eight million merchants who accept credit cards in the whole country. Square is using a growing number of retail partnerships to push sales of its card reader, most recently T-Mobile.