Square Inc. has introduced its much-anticipated payment card acceptance software application for Apple Inc.'s iPhone.

The free software became available Tuesday via Apple's iTunes online store.

In April the San Francisco company rolled out a version for Apple's iPad.

Square has generated plenty of buzz since proclaiming late last year that it would "revolutionize" the payments industry with a device that enables small merchants and even consumers to use mobile phones to accept cards.

But Square appears to have raised the service's merchant rates since April by adding a fee of 15 cents per transaction to the card-present rate of 2.75% of the sale and the card-not-present rate of 3.5%.

A Square account has no setup costs or monthly fees.

The account sign-up process also mimics the information sought by other independent sales organizations by asking for a user's name, address, Social Security number and birth date to perform a credit check.

Square sets account limits that it may adjust once a user completes additional identity or credit-verification processes with the company, according to the terms of service posted on its website.

Square is included on Visa Inc.'s list of registered independent sales organizations.

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