Square Inc. is shooting for a mass rollout of its much-delayed mobile payment service by late summer.

The San Francisco company released a beta version of its service to a small number of merchants in December and originally intended to roll out its product more broadly early this year. In June, its chief executive and co-founder, Jack Dorsey, e-mailed customers to say the mass rollout was going to be delayed indefinitely, because of hardware shortages and the need to strengthen fraud management capabilities.

The rollout is now getting back on track. "We are wrapping up the pilot program now," Dorsey said in an interview. He was the founder of the social media website Twitter Inc.

Square lets people accept payment cards with mobile devices.

Dorsey said the company has learned a lot about fraud prevention. Square sponsors merchant users and fronts them money.

Over the past few months, Square has been building and testing software that flags irregular transactions as well as other tools that authenticate the identity of a credit card user.

Square said it solved its hardware issues after co-founder Jim McKelvey was dispatched to China to deal with manufacturing bottlenecks. Dorsey said Square now has the ability to make 10,000 daily of its namesake square card reader devices that plug into phones.