Gone are the days of paper invoices, checks and cash when it comes to charging customers for services out in the field. Smartphone add-ons such as the ones put out by Square and Intuit have made accepting plastic as easy as punching in a few numbers and swiping your customer’s credit card, even for small businesses.

Available on the iPhone, iPad and Android (Intuit’s GoPayment is also available on BlackBerry) the Smartphone add-ons are a far cry from the clunky swiping machines techs used to have to lug around, that is, if they even accepted credit cards at all.

“GoPayment is ideal for people who want to sell products and services no matter where they are – on the road, at events or in the field,” GoPayment Product Manager Andrew Freed recently told AllBusiness. “For field service businesses, it lets business owners add up to 50 employees to one GoPayment account so that their employees can process credit cards on their mobile phones.”

The service is also suited for brick and mortar businesses that simply want to enable their employees to take credit card payments while on the store floor.

The services offered by Square and GoPayment are similar. Though GoPayment used to charge for its card readers and a $13 monthly fee, it recently began offering both for free to compete with Square, reports Fortune’s Michal Lev-Ram. While Square’s stamp-sized readers fit into a phone’s audio jack and are a bit less rugged than GoPayment’s slim scanners that actually look like an extension of the phone itself, both make money by taking a cut out of each credit card transaction.

GoPayment’s got two different service plans, one that charges low-volume customers 15 cents per swipe and 2.7 percent of the total and one that charges high-volume customers 30 cents per swipe and 1.7 percent of the total. The high-volume plan also cost a monthly fee of $12.95. Meanwhile, Square offers one plan that charges customers a 15 cent transaction fee and 2.75 percent of the transaction. Each service may have its own advantages but both add a valuable tool to any field service tech’s tool belt.

More on mobile field service technology on The SmartVan.

ABOUT Sara Suddes

San Francisco-based contributor Sara Suddes writes frequently about small business, the economy and technology.