No, not every traveler needs one — but here’s how to find out if you do.

When you arrange a flight online, there’s quite a bit of information you need to provide, from your email and phone number to your frequent flier number if you have one to your credit card details. It’s fairly obvious as to what most of this is, but there’s one piece that sometimes confuses travelers: a redress number. So, what is a redress number, and do you need one to travel? Here’s what you need to know.

What is a Redress Number?

A redress number, formally referred to as a Redress Control Number, is issued to travelers who are part of the Department of Homeland Security’s Traveler Redress Inquiry Program (DHS TRIP). This number is crucial in helping travelers alleviate recurring security issues. Some travelers may find themselves regularly selected for secondary screening or experiencing issues at the U.S. border. Therefore, a redress number alerts the Transportation Security Administration (TSA) that a traveler may be incorrectly added to a security watch list, which could happen on occasion.

Do You Need a Redress Number to Travel?

No, travelers do not need a redress number to travel. However, if you find yourself frequently encountering security issues when flying or crossing the U.S. border, it may be advisable to apply to DHS TRIP to smooth out the travel process. According to the DHS, “People who have been denied or delayed airline boarding; have been denied or delayed entry into or exit from the U.S. at a port of entry or border crossing; or have been repeatedly referred to additional (secondary) screening can file an inquiry to seek redress.”

How Do You Get a Redress Number?

You can apply for a redress number at trip.dhs.gov. The website also features a helpful quiz to assist you in determining whether or not you need a redress number. Keep in mind, rejection based on your application may occur.

Is a Redress Number Different from a Known Traveler Number (KTN)?

On flight reservation forms, spaces for redress numbers and KTNs are typically located near one another or sometimes even on the same line; however, they serve different purposes. While redress numbers are meant for travelers who have successfully applied to DHS TRIP, KTNs are part of the Global Entry and TSA PreCheck programs, which expedite entry at U.S. borders and TSA airport security, respectively. Consequently, more travelers possess KTNs than redress numbers, but it’s entirely possible to have both.