The way we pay for things is changing. Those credit-card keypads yielding paper receipts are giving way to a new group of mobile payment devices that merchants say charge cheaper swipe fees, and are faster and easier to use.

Recently, Starbucks signed on with Square, one of the more popular devices in the market. That means 7,000 Starbucks stores will process U.S. credit and debit card transactions with Square – thus linking the card reader with a major retailer.

An array of other devices are on the market, including Intuit GoPayment and PayPal Here. Others in the mobile payment mix include Groupon and Google. Several large retailers, including Wal-Mart, Best Buy, Target and others, recently announced they’re joining forces on their own upcoming mobile payment method.

Here’s how these systems generally work: Commerce companies provide a free card reader to retailers, who plug it into the headphone jack of their mobile phone. After customers get their card swiped, they sign receipts with their finger, and have the option to leave tips. Receipts are sent by text or email. Merchants are charged a percentage per swipe, with the remaining money from the purchase deposited into their account.

In Charlotte, more than 5,000 individuals and businesses accept payments with Square, according to Lindsay Wiese, who works in communications for the San Francisco-based commerce company. Representatives for PayPal and Intuit said their companies don’t provide specific merchant data by region.

Square seems to be the predominant device of choice in Charlotte’s food truck circuit, where some use the iPad version, called Square Register, which allows sellers to keep inventory of sales.

During certain stretches of the weekly Food Truck Friday in Historic South End, “I can also track what are my top sellers,” said Emma Merisier, owner of SouthernCakeQueen, who uses the iPad version on her pink truck. “That can help me decide what cupcakes I’m baking for the following week.”

Wayne Parker, with Whispering Willow bath and beauty products, thinks using Square generates more business at fairs and at his station inside Atherton Market on South Boulevard. After one customer confirmed that his business takes credit cards, she spent more than $100 in gifts. “It definitely has made a difference (in) the amount of business we’ve been able to do,” Parker said.

Some brick-and-mortar retailers say they became tired of other point-of-sale credit-card systems that included hefty bank processing fees. Jason Glunt, owner of Salud Beer Shop in NoDa, said he’s saving about $250 a month by using Square. “For me, for what I do, it’s perfect,” Glunt said. “I’d rather spend my money on product, not on some fancy checkout system.”

Larry Swayne, with Wingzza wings and pizza food truck, is sold on Intuit GoPayment’s organization. He said Intuit approached him about trying its system, and he immediately took to the way it links with Intuit QuickBooks, the small-business accounting software. He has been using a more traditional reader system with paper receipts.

He said Intuit is faster and more convenient, and his customers like it, too. “Customers have become used to paying that way, so it’s not that much of a new thing.”

Mobile payment systems aren’t foolproof, though – they’re at the mercy of how fast phones and tablets can process the cards. Plus, systems can go down, meaning lost business among customers who no longer carry cash.

Some retailers worry about customers questioning guarantees that credit card information remains private.

And some merchants are surprised when there are delays with their deposits, which can run from one to three days, or longer, they say.

Tom Bartholomy, president of the Charlotte-based Better Business Bureau of Southern Piedmont, said that delay comes from some of these companies taking more time reviewing transactions, compared to banks, which may work faster.

Still, “it’s a great market for merchants right now because there are a lot of players in the marketplace,” Bartholomy said. “So they can shop the rates, and all the fees associated with it, and do Google searches, BBB searches, and see what other merchants are saying about them.”

Heidi Bancker with Napolitano’s food truck is keeping her options open. She started with Intuit GoPayment because of its compatibility with QuickBooks, and recently adopted Square, which she says has a more streamlined system for getting merchants their money. She keeps both systems, so she’ll have a backup in case one goes down.

Bancker also just started using LevelUp, new on the Charlotte scene. Customers use their phone to take a picture of their credit card, which converts the image into a unique QR code. Merchants with readers can pick up the customer’s code for payments.

Bancker said she’s used LevelUp twice already. “It’s super easy, it’s fast,” she said. “We have it on the truck if anybody has it.”