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It takes money to make money, or so the saying goes. And Square, the e-commerce start-up, wants to make a lot more money.

The company recently closed a venture financing round of $150 million, according to a person briefed on the investment, who spoke on condition of anonymity because he was not authorized to speak publicly. The round values Square at $6 billion, the person said.

This latest round, which was led by a new investor, the Government of Singapore Investment Corporation, places Square in the company of Internet start-ups like Pinterest and Spotify, which also have valuations around $5 billion to $6 billion. Some previous investors, including Goldman Sachs and Rizvi Traverse Management, also participated in the round, according to this person.

Last month, a filing disclosed that Square had planned to raise at least $100 million in venture capital, though at that time the round had not closed.

A Square spokesman confirmed the company had closed a round of financing, though he did not comment on the valuation, amount raised or participating investors.

“We stand for independent businesses and will continue to invest aggressively to empower them with tools that help them grow,” the spokesman said.

The move comes amid a time of great tumult in the payments industry. Apple, the consumer technology giant, introduced its new commerce product, Apple Pay, along with its new smartphones, the iPhone 6 and 6 Plus. Ebay announced that it wouldspin off PayPal, the company’s big payments business. And in August, Amazon introduced its own version of a credit card reader, which has a low processing fee rate to lure new merchants.

These companies and their assorted products compete with Square in some form or another. And compared to Square, all of them have far more access to money to back their efforts.

Square, a six-year-old start-up, spent much of its early years giving away free credit card readers to small and medium-sized businesses, asking for 2.75 percent of each transaction using the reader. The small dongle, square in shape, became especially popular with merchants who had conducted mostly all-cash operations.

Recently, however, Square has tried to diversify its revenue streams beyond its core payments business. In May, the company introduced Square Capital, a cash advance program for small businesses. Square acquired and continues to run Caviar, a start-up that provides food delivery for restaurants that do not otherwise offer it. And Square offers an appointment booking service to small businesses for a monthly fee.

Still, Square’s road ahead is not easy. PayPal has increasingly stepped up its marketing efforts on PayPal Here, its own credit card reader, as well as PayPal Working Capital, the company’s cash advance program. And Amazon plans to keep its credit card processing fees lower than Square and other competitors for the long-term.

Square will introduce a new card reader that is compatible with E.M.V. microchip technology, a more secure form of processing credit cards that is set to become the standard. It also plans to accept Apple Pay payments, which could increase transaction volume if the new form of payment takes off.