First class mail tracking number start with

First Class Mail tracking numbers in the United States typically start with the following prefixes:

• 920 (for domestic mail)
• 930 (for international mail)
• 940 (for international mail with a customs form)
• 950 (for international mail with a customs form and insurance)

For example, a First Class Mail tracking number might look like this:

• 920123456789
• 930123456789
• 940123456789
• 950123456789

Keep in mind that not all First Class Mail pieces have tracking numbers. Tracking numbers are typically assigned to mailpieces that are sent with a tracking service, such as USPS Tracking or Signature Confirmation.