With the rise of professional internet scalpers, forged concert tickets are becoming an ever greater problem. Collectively, these vultures push popular shows into selling out, and then resell the tickets at exorbitant prices. For the most part, they never meet their customers. Some combine scalping with forging, making scalped tickets a very dodgy proposition indeed. However, there are a few ways to check the authenticity of a ticket.
Ask to see a purchase receipt along with the original credit card. This is a good way to see if the scalper actually bought the tickets. But it is unlikely even the most honest scalper will be willing to verify a credit-card number in a virtually anonymous credit-card transaction. This step can be applied to physical or e-tickets.
Insist on getting the ticket's serial number. All event tickets that are not sold at the ticket window on the day of the event come with a bar code and serial number. You can use this to verify the validity of the ticket with the issuing company, such as Ticketmaster. This will also help you as a follow-up step in avoiding the other fake ticket scam: the ticket that was real, but has been reported lost or stolen in order to secure a refund. This step can be applied to physical or e-tickets.
Make a physical comparison between the suspect ticket and a recent, valid ticket from the same vendor. This is unlikely to catch a sophisticated forger, but many forgeries are actually not that sophisticated and can be caught with a through examination under a magnifying glass. Also check the paper quality and texture. This step can only be applied to physical tickets.
There is an urban legend that if the corner of a fake ticket is heated and turns black, it is genuine. Attempting this test won't accomplish anything, but it could set your ticket on fire, valid or not. Do not try heat or flame testing a concert ticket.