I have gotten the GS discount when using a credit card. I have also gotten the discount when using a check. There are still campgrounds that do not accept credit cards but will accept a personal check. These are usually the Mom and Pop campgrounds. So do not be so quick to throw out those left over checks. It costs the campground a lot of money to accept credit cards. I have even received the Good Sam discount at a private non-Good Sam campground that only accepted personal checks. They said it was a reward for campers that supported the RVing life by being a Good Sam member.