And transactions value is now on target to hit $6 billion this year.
There's little doubt that credit card dongle specialist Square is one of the genuine stars of the mobile market right now.
It's the original pioneer of the drive to turn iOS and Android devices into card processing machines and as such it's massively disrupting the retail payments space.
Merchants seem to love it. More than two million businesses and individuals use the transaction platform, up from one million six months ago.
This has prompted Square to up its projection for annual transaction value from the $5 billion reported in April, to $6 billion.
It's all very impressive, but then Square needs to perform as it's bagged around $137 million from investors so far.
And it has no shortage of competition from small start-ups like iZettle and Swiff, and also big corporates like PayPal and Intuit.
Square charges a flat fee of 2.75 per cent on all transactions, with no contracts or monthly fees or hidden costs.