Check your TSA PreCheck or Global Entry approval documents
Look at your Trusted Traveler Program membership card if you received one
Log in to your Trusted Traveler Program account on the official CBP website
Find your Known Traveler Number in your account profile or membership details
Review past airline boarding passes if your KTN was saved there
Check confirmation emails from TSA PreCheck, Global Entry, NEXUS, SENTRI, or FAST enrollment
Contact the Trusted Traveler Program help desk if you cannot locate it
Ask your airline if your KTN is stored in your frequent flyer profile