The number on your passport is similar to the number on your driver's license. It is a distinctive number that separates your passport from every other passport that has been issued. If you want to check your passport to find out which is the proper identification number, you can do so in a few seconds. You might need to know this number if you're filling out forms before, after or during a trip.
Open your passport booklet, revealing the information on the inside.
Flip to the page in your passport that contains your picture. If you have a passport card and not a regular passport, the picture will be on the front of the card.
Look at the number in the top-right corner of both your passport page or your passport card (whichever is applicable). The number in this location (which will be either 9 or 10 digits, depending on when your passport was issued) is your passport ID number.