Why Is Your USPS Tracking Number Invalid?(+Solutions)

Have you ever entered a USPS tracking number into the tracking service and then found out that it is invalid? If so, you’re probably feeling confused, frustrated, and possibly pretty concerned about where your package could be!

There are a few potential explanations for a tracking number not working, including the fact that your package hasn’t been scanned properly, or that the tracking information has been sent to you incorrectly. Alternatively, your tracking number could be missing a digit.

In general, USPS tracking numbers should work reliably and provide fairly accurate updates as to where your package is and how soon you can expect it. Even with the best systems, however, things go wrong sometimes – so let’s find out more about this.

What Does USPS Invalid Tracking Number Mean?

An invalid tracking number means that the USPS tracking system is failing to recognize the number you are providing, and cannot attach it to a package for some reason.

There are a few potential explanations for this, but it’s a very frustrating error to encounter, especially if you are waiting for an urgent package.

If you get this error, you will need to check you have the full tracking number right before you do anything else.

Entering only part of the number will result in this error appearing.

Why Is The USPS Tracking Number Not Working?

Usually, a tracking number that doesn’t work has simply been incorrectly entered into the system.

If you are copying and pasting the number from somewhere, make sure it is pasting correctly. If you are typing it up, check you haven’t missed a digit.

If you are sure you have entered the number correctly, get in touch with the sender to double-check that the number was free from errors when it was sent to you.

If you are the sender, go back to your original receipt from the post office and make sure you haven’t made any mistakes when copying it up.

You should also double-check that you are using USPS’s tracking system, not the tracking system for another mailing service. These systems are not interchangeable, and a USPS number won’t work on another business’s tracking system.

Some alternative explanations may be that the USPS tracking system is down, and if you try again later, the error will have resolved itself.

In some cases, an invalid tracking number indicates that the sender is scamming you and has never actually mailed a package. Alternatively, they may be in another country and the tracking may only become available when the item reaches your country.

What Is A Valid Tracking Number For USPS?

In general, a USPS tracking number will be 22 digits long, and these digits will appear in groups of four. Some are only 20 digits long.

No USPS tracking numbers should have letters in, except for USPS Express Mail tracking numbers, which are 13 digits long and will start with two letters, and then end with the letters US.

If your tracking number does not look like this, it is not a valid USPS tracking number. Some examples are below:

  • 9500 2000 1000 0000 0000 00
  • 9004 1000 2400 0003 0000 00
  • 3178 3030 1001 0020 0010 00

Check your tracking number against these for the same pattern and number of digits, and if in doubt, get in touch with the sender to ask them to check that they have sent the tracking number correctly.

How Long Does It Take For The USPS Tracking Number To Show Up?

If your sender has already informed you that they have dispatched the package, and it isn’t yet showing up for you, you might be feeling confused about why your tracking number doesn’t work.

Usually, packages are scanned as soon as they are handed to USPS, so it should start working immediately.

However, it can take up to 24 hours for a tracking number to start working after the item has been scanned. This is annoying, and it won’t always happen, but it’s worth being aware of this potential issue.

It is also possible that the item didn’t get scanned when it was handed to USPS.

This sometimes happens if the workers are very busy or if the equipment doesn’t read the barcode properly and the member of staff doing the scanning doesn’t notice.

This could result in the tracking number taking longer than 24 hours to start working, but it should start once the package gets scanned at its next destination.

Packages usually get scanned multiple times as they travel, so don’t worry if yours won’t show the tracking information straight away – it will usually do so later.

What To Do When The USPS Tracking Number Doesn’t Work?

Usually, the first thing to do if your USPS tracking number doesn’t work is check that you have entered it correctly and then get in touch with the sender.

If the sender says that the tracking number is correct, show them the error you are getting with USPS’s tracking software, and ask them to follow up.

The sender can get in touch with the post office and find out why the tracking number is invalid.

They should then get back to you about what has happened and hopefully provide a fix.


Your USPS tracking number may be invalid because it has been entered incorrectly, or because the item has not yet been logged in the system.

Sometimes, other issues, like international shipping, could cause a tracking number to show as invalid.