A USPS tracking number not working usually means USPS can’t match the number to a record: it was mistyped or copied incompletely, it belongs to another carrier, the package hasn’t had its first scan yet, or the record has expired after 120 days. Check the number against the label or receipt first, because a single wrong character returns an error even when the package is moving normally.
This page covers numbers that USPS rejects or can’t find. If your number loads but the status hasn’t changed in days, that’s a different problem, covered in our guide to USPS tracking not updating.
Why Is My USPS Tracking Number Not Working?
An error on the tracking page has a short list of causes. Each one has a different fix, so it helps to pin down which one applies before contacting anyone.
| Cause | What you usually see | Fix |
|---|---|---|
| Typo, missing digit or extra space | Invalid number or no record found | Copy and paste from the receipt or label |
| Not a USPS number | No record found | Check the format and track with the right carrier |
| No acceptance scan yet | Label created or status not available | Wait about 24 hours after drop-off |
| Order or receipt number instead of tracking number | Invalid number | Find the full tracking number on the label or receipt |
| Record older than 120 days | No record found | Use your saved records or proof of delivery |
| Website or app glitch | Errors for every number you try | Switch channels or retry later |
If the page returns errors for every number, not just yours, the tracking system itself may be having trouble. Our page on whether USPS tracking is down explains how to confirm an outage.
What Does a Valid USPS Tracking Number Look Like?
Most domestic USPS tracking numbers are 20 to 22 digits and usually start with 9. International USPS numbers are 13 characters: two letters, nine digits and “US.” If your number doesn’t fit either pattern, it may not be a USPS number at all.
| Service | Sample format | Length |
|---|---|---|
| USPS Tracking (most packages) | 9400 1000 0000 0000 0000 00 | 22 digits |
| Priority Mail | 9205 5000 0000 0000 0000 00 | 22 digits |
| Certified Mail | 9407 3000 0000 0000 0000 00 | 22 digits |
| Priority Mail Express | 9270 1000 0000 0000 0000 00 or EA 000 000 000 US | 22 digits or 13 characters |
| Priority Mail International | CP 000 000 000 US | 13 characters |
These are USPS sample formats, and the first digits vary with the system that printed the label. Our guide to what a USPS tracking number starts with explains the prefixes, and our USPS tracking ID guide shows where each number is printed.
A number starting with “1Z” is a UPS tracking number, and other formats may belong to a retailer’s delivery partner. Those won’t work on usps.com even though the package is moving.
How Do You Fix a USPS Tracking Number That Isn’t Working? 7 Fixes
Work through these in order. The first three solve most errors in a few minutes.
1. Copy the Number Instead of Retyping It
Paste the number straight from the receipt, label or shipping email, then delete any spaces, dashes or trailing characters. In international numbers, watch for the letter O typed as zero, and confirm the two letters at each end are there.
2. Make Sure You Have the Full Tracking Number
Receipts and order emails often show several numbers. The tracking number is the long one printed under the barcode, or labeled “USPS Tracking #” on a Post Office receipt. If you’ve lost the paper copy, our guide to finding a USPS tracking number from a receipt shows what to look for.
3. Confirm the Carrier
Ask the sender which carrier shipped the package, or look at the number’s format. A store may hand a parcel to a delivery partner first, and USPS can only show a status once it has the item.
4. Wait 24 Hours After Drop-Off
A new label has a tracking record, but USPS can’t show movement until the package is physically scanned. Items left in a collection box or handed over late in the day are often scanned the next business day. If you see a “not available” message rather than an invalid-number error, see what “USPS tracking is not available” means.
5. Try Another USPS Channel
The USPS website, the USPS Mobile app and text tracking all read the same record. Text the number to 28777 (2USPS), or call the USPS tracking line at 1-800-222-1811. If the website errors out but text tracking works, clear your browser cache or switch browsers.
6. Check Whether the Record Has Expired
USPS keeps standard tracking records for 120 days, after which the number stops returning results. Signature Confirmation records are kept for one year, and Priority Mail Express, Certified Mail and Registered Mail records for two years.
7. Contact the Sender, Then USPS
If you’re the recipient, ask the sender to confirm the number against their own receipt and the date it was mailed. If the number is correct and still fails a week after mailing, USPS lets you submit a Missing Mail search starting 7 days after the mailing date. Our guide to USPS tracking number customer service covers what USPS can and can’t look up for you.
Why Does a Tracking App Say USPS Tracking Requests Are Limited?
A message saying USPS tracking requests are limited, often with a prompt to unlock more requests, comes from a third-party tracking app or website, not from USPS. Outside services pull tracking data from USPS’s systems, and when that access is capped or changed, the app can’t refresh your number even though the number is valid.
The fix is to skip the middleman. Look the number up on usps.com, in the USPS Mobile app or by texting it to 28777, which read the tracking record directly. You don’t need to pay for or “unlock” anything to track a USPS package with USPS.
Can You Track Several USPS Numbers at Once?
Yes. The USPS tracking tool accepts up to 35 numbers in one search, separated by commas or line breaks. If a batch fails, one malformed number in the list may be the cause, so try the numbers one at a time to find it.
QR codes on Post Office receipts can also open the tracking page directly, which avoids typing errors. Our guide to the USPS tracking QR code explains how that works.
How Can Shippers Avoid Tracking Number Problems?
Most invalid-number complaints start with how the number was shared. Send recipients the full number by copy and paste, and include a direct tracking link where you can.
- Save every receipt and label record until the package is delivered.
- Print labels clearly, with the barcode flat and away from box seams, so the first scan happens on time.
- Hand packages over at a Post Office counter or a scheduled pickup when you need a same-day acceptance scan.
- Tell recipients which carrier you used, especially if you ship with both USPS and UPS.
If you print labels with ParcelPath, each USPS label carries standard USPS tracking and is saved in your shipping history, and you can schedule free USPS pickups. ParcelPath is free, with up to 89% off USPS and up to 85% off UPS, and you can compare both for a package in the ParcelPath rate calculator.
For background on how scan data flows into tracking, see our explainer on what USPS tracking is, our overview of package tracking services, and our list of USPS services and shipping options, most of which include tracking that starts with the first scan.
Frequently Asked Questions
Why does USPS say my tracking number is invalid?
USPS shows an invalid-number error when the characters you entered don’t match a tracking record. The most common reasons are a typo, a missing digit, an order number entered instead of the tracking number, or a number from another carrier. Copy the full number from the label or receipt and try again.
How long until a new USPS tracking number works?
A new USPS tracking number usually shows a label-created status right away and a movement status after the first physical scan. Allow about 24 hours after drop-off, longer if the package went into a collection box or was handed over after the last collection time.
Can a USPS tracking number stop working after delivery?
Yes. USPS keeps standard tracking records for 120 days, so older numbers eventually return no results. Signature Confirmation records last one year, and Priority Mail Express, Certified Mail and Registered Mail records last two years. Save a screenshot of the delivery status if you may need it later.
Why does my USPS tracking number work in one app but not another?
Third-party tracking apps depend on data they pull from USPS, so they can lag or stop updating when that access is limited. USPS.com, the USPS Mobile app and text tracking at 28777 read the USPS tracking record directly, so check there before assuming the number is wrong.
Sources
- USPS FAQ: USPS Tracking, The Basics
- USPS FAQ: How to find your tracking number
- USPS: Contact Us (tracking line)
- USPS: Missing Mail
Part of our USPS Tracking guide. Related: USPS Tracking and Delivery, USPS Tracking Not Updating, USPS Tracking Not Updating After Drop Off.
