Square, the financial-services startup that helps small businesses process credit card payments, is planning to go public.

The six-year-old company is known for its white, cube-shaped card readers that plug into smartphones and tablet computers, turning them into electronic sales terminals. It's also known in the tech industry for being founded and led by Jack Dorsey, 38, who was separately named CEO of the social networking service Twitter last week.

Dorsey, who owns 24.4 percent of Square, co-founded Twitter in 2006 and has said he'll continue to run both companies.

Square filed regulatory papers on Tuesday for an initial public stock offering valued at up to $275 million, although that figure could change. While some larger tech startups have recently delayed going public, Square's filing has been expected and records show the company previously filed a confidential declaration of its plans over the summer.

San Francisco-based Square says it had $850 million in revenue last year. Revenue for the first half of this year was $560.6 million, an increase of 51 percent over the same period last year.

But the company had a net loss of $154.1 million in 2014, and a loss of $77.6 million for the first half of 2015; overall, it's piled up an accumulated deficit of almost a half billion dollars since its inception. It warned that it may continue to generate losses as it invests to expand the business. Square also warned that a major customer, Starbucks, is planning to stop using its service sometime before the third quarter of 2016.

Square has added new services in an effort to diversify its business over recent years. The company provides financing to small businesses and a payment service known as Square Cash that lets individuals and businesses transfer funds to each other. It also operates Caviar, a food delivery service for restaurants.

--Associated Press