NEW YORK (CBS/AP) — Square, the six-year-old company known for its white, cube-shaped card readers that plug into smartphones, is boosting its planned initial public offering value by 47 percent in what has become a very rocky market for new companies trying to raise cash.

The San Francisco financial-services startup was founded and is led by Jack Dorsey, who co-founded Twitter and recently returned to lead that company again.

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Square Inc. plans to offer just over 31 million shares at $13 apiece for about $403.7 million. Previously, the company had filed regulatory papers for an IPO valued at up to $275 million.

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Square helps small businesses process credit card payments and tablet computers, turning them into electronic sales terminals.

Shares will trade under the symbol SQ on the New York Stock Exchange.

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