NO there no fee involved except what you pay for the certifacate. I purchased a $25 credit for a local place here that normally would have been $10 after the 60% off it cost me $4. When we went we had to "spend" $35, we (me dh & dd) all had a soda, shared a appetizer, each had a meal, and than shared a dessert. The check was for $36 and change after they took off the $25 the bill was $11 and change. So we got $36 worth of food for $15 + tip. That's a great saving !
It's worth a look. My parents favorite Japanese restaurant is on the site so it's like a 2 for 1 coupon for them.