How do you handle clients obviously lying about their dogs age?

So, in my case, I always ask that the owner bring the most recent rabies vaccination record from their vet with them or upload a photo of it to the booking. This makes sure that:

1) I have proof of rabies vaccination in case of emergency 2) I know that the dog is the appropriate age 3) I know that the dog has a vet

By asking for this, I've never had someone try to sneak in a puppy at the adult price range. But it also provides peace of mind for me, knowing that I have taken steps to ensure the health of my dogs and any dogs boarding with me. I have had owners tell me that they don't have their most recent vaccination records. In this case, I just ask for the vet information that administered the vaccinations and get their permission to call and verify the shot records. Owners that won't comply with this request aren't really the type of pet-parents I want to work with. Most good, responsible pet owners will understand that the hoops are in place to ensure the safety of their pets as well.