Counterfoil
/ˈkaʊntərfɔɪl/
Definition 1 of 1
Pro Tip 1/3Record Keeping
A counterfoil is part of a physical record system, helping with tracking transactions or entries. 
After writing the check, I filed away the counterfoil as evidence of the payment.
Pro Tip 2/3Proof of Purchase
Keep your counterfoil safe; it often serves as proof that you bought or paid for something. 
The shopkeeper asked for the ticket counterfoil to confirm my purchase for the warranty.
Pro Tip 3/3Physical Ticketing
Counterfoils are more common in physical ticketing systems, not in digital ones. 
For the raffle, they gave me the counterfoil, and I watched as they put the main ticket in the drum.