As you can see his sign indicated $19.99 for smog check. So you have to show the $17.99 smog check in your phone app in order to get a discount. Beside there a lot of smog place you can get same $ for the smog check and they give you drink or some places free car wash. The guy smog checked my car and when the payment came, he asked for the tip. I never had anyone ask for the tip. When I said, no thanks he looked at me with very disappointed face. When I paid with credit card, he charges $1.00 extra as well. That would be my last time going here to get smog check. There are so many smog place in Las Vegas, you need to be nice to your customer.