Business owners must understand the status of a shipment so they can share it with their customers. The U.S. Postal Service (USPS) includes automatic tracking in most of its domestic shipping options so that you can track your packages as they make their way to their destinations. USPS shipping labels come with a tracking code. The first four digits indicate the type of mail service you're using.


The first four or five digits in the tracking number comprise the service code. These numbers denote the type of mail service you're using, and there are hundreds of permutations.

Anatomy of a Tracking Number

Your package may be scanned up to 13 times during its journey from your warehouse to the customer, and you'll be notified of the package's location each and every time it is scanned. The tracking number is the unique identifier for your package. Most USPS tracking numbers are 22 numbers long, arranged in groups of four digits, such as 9400 1234 5678 9999 8765 00. However, there are many formats, among them tracking numbers that start with the letters "EC" or "CP," which indicate that the package is being mailed overseas.

Understanding the First Four Digits

The first four, and sometimes five, digits comprise the service code. These numbers denote the type of mail service you're using. For example, the USPS gives the following tracking code format examples for its popular mail services:

USPS Tracking: 9400 1000 0000 0000 0000 00
Priority Mail: 9205 5000 0000 0000 0000 00
Certified Mail: 9407 3000 0000 0000 0000 00
Registered Mail: 9208 8000 0000 0000 0000 00
Signature Confirmation: 9202 1000 0000 0000 0000 00

There are hundreds of service codes covering all possible permutations of USPS services. USPS has published a full list of services in USPS Publication 199.

How to Track a USPS Package

For customers, the format of the tracking number is not especially relevant. The critical issue is that you keep a note of the tracking number so you can find out where the package is on its journey. You'll find the tracking number in a few different places depending on how you mailed the package. If you dispatched the shipment through a post office, for example, it will appear on your sales receipt and on the peel-off portion of your USPS tracking label. If you printed the label through an online service, it will appear on the dashboard of your online account. To track your package, navigate to the USPS tracking webpage and enter your tracking number. You can enter up to 35 numbers at any one time.

Tracking Tips

Place your shipping labels in a visible place so the bar code is easy to scan. Scanners can't see around the curvature of tubes or the edges of a box, so if you place your label in these locations, you will never get any tracking events for your package. Place the label in as flat a location as possible, and avoid placing it over seams as the label can split.