Daily deals specialist Groupon has entered the mobile payment game with hopes to gain market share by undercutting the competition. The new service, Groupon Payments, is built into the latest version of the Groupon Merchants app for the iPhone and iPod touch and will allow merchants to run credit card payments much like key competitor Square in addition to being able to scan and redeem Groupons.

The nationwide rollout comes after a successful pilot program for Groupon in the San Francisco Bay Area earlier this year. Rates for swiped transactions using an audio jack accessory or case-based card reader are as follows: MasterCard, Visa and Discover will be charged 1.8 percent plus a $0.15 fee per transaction. American Express is a bit more expensive at 3 percent plus the same $0.15 per transaction fee.

Groupon says there are no hidden costs or monthly fees and merchants will have their credit card payments deposited into their bank accounts overnight versus having to wait a few days with the competition. For comparison, Square charges a flat rate fee of 2.75 percent on transactions regardless of which company backs the plastic.

The only catch, if you would even call it that, is that merchants are required to run deals with Groupon to lock in these low transaction rates. The company notes there’s a pilot program for non-Groupon merchants with a set fee of 2.2 percent for the big three card companies and 3 percent for American Express, in addition to the mandatory $0.15 per transaction charge.