Looking at the bars printed at the bottom of the letters I received last week made me realize I’d never spent as much time learning about these Intelligent Mail barcodes as intended. When I got my first credit card in the mail, Amex emailed me when it was out for delivery and had been delivered. Being an entry-level, Blue Cash Everyday card, they’d only sent it via regular, First-Class Letter service, which, as far as I knew, wasn’t tracked.
As it turns out, these letters1 can be tracked! The tracking isn’t as detailed as that of packages, and there aren’t always out-for-delivery or delivered updates,2 but it’s a massive improvement over the “drop it in the collection box and cross my fingers” method I’d been using.
There are websites that charge per letter to do this, and downloadable paid software to streamline generating and cataloging your IMb codes,3 but it’s more fun to do it yourself.
(After publishing this, I found a free tool that does ~all of the work for you. It’s easier to set up, and its tracking interface is better for at least some use cases.)
It took me a bit to understand how I could do this myself: the information was scattered around various corners of the internet (maybe interest in using Intelligent Mail barcodes to track your personal mail is relatively low), so here is my attempt at an all-in-one guide!
What is an IMb?
An IMb is a barcode the USPS uses to track and sort letters, among other things. It’s 31 digits long and follows4 the format shown in the following image.

If you’ve noticed the number sometimes printed at the bottom of your mail, you might have realized that buildings in the US can be identified by an 11-digit delivery point ID, AAAAABBBBCC, where A stands in for each digit of the 5-digit ZIP code, B for each of the extra four (ZIP+4), C for the last two of the building number. For example, the delivery point ID for 10401 Post Office Blvd Fl 2, Orlando, FL 32862 is 32862854201. There is only one building in this ZIP+4, so the delivery point ID isn’t any more specific. Generally, though, the ZIP+4 will represent a handful of houses on one side of the street. In this case, the delivery point ID would refer to only one address because the last two digits of a building number shouldn’t repeat within a ZIP+4.
You can use this tool from Melissa to look up ZIP+4s and create delivery point IDs.
Note that the routing code doesn’t have to include the full 11 digits, nor is it even required. I always include it to help with sorting, but that requires each barcode be customized for each address. If you’re only interested in tracking, you can leave out the routing information.
Making an IMb
To generate IMb codes, you need a mailer ID. USPS makes obtaining one seem grander than it is. When they say you need to “apply” for a mailer ID, they mean to say that you need to be able to type information into a web form and hit submit before automatically being granted one. And you, dear reader, are your own “designated Business Service Administrator.”5
- Make a USPS business account here.
- This can’t be shared with your personal account (e.g., if you order stamps online or use Informed Delivery).
- You can list your home address and respond with your name when it asks for that of your business.
- You can follow more detailed instructions here.
- Once you’ve reached the BCG homepage, click “Mailing Services” in the top-left, and click “Get Access” next to “Informed Visibility.”
- Find your mailer ID by clicking “Go to Service” next to “Mailer ID” that same page, or by navigating to mid.usps.com.
- It is not the number above your “company address.”6
- Visit the USPS IMb Encoder/Decoder, and click on the “Encoder” tab.
- Assuming your mailer ID is 9 digits, select that radio button.
- The barcode ID should always be “00.”
- For a regular letter with tracking, enter “310” in the “Special Services” field.
- This number should be the Service Type ID (STID), which you can find listed here. 310 is the STID for basic/nonautomation7 First-Class Mail with tracking but without address correction.
- The STID is not to be confused with the Content Identification Number (CIN), which is also three digits and is required by the Intelligent Mail Barcode Generator (IMBG) tool. Both the CIN and the IMBG are completely irrelevant for our purposes.8
- You get to make up the serial number and can use an Excel sheet or something to track them. Assuming your mailer ID is 9 digits, your serial number will be 6 digits. You can start with zero and number them sequentially, generate them randomly, or do something else; it’s yours. Enter it in the field.
- Enter the delivery point information if you’re using it.
- Press “Encode.”
- Save the image of the IMb, and print it on an envelope, address label, or similar; or
- Download and install the USPS IMb font from PostalPro
- In the ZIP file, it’s “USPSIMBStandard” in fonts → scalable → trueType
- Paste the string of barcode characters (some combination of A, D, F, and T) into Word or a similar program
- Set the font to USPSIMBStandard, and change the size to 16 or 17pt, as recommended by USPS
- Download and install the USPS IMb font from PostalPro
- You can print the barcodes directly on envelopes, or on stickers or pieces of paper. You can print the address with each barcode, but you don’t have to; you may also hand-write addresses.
The IMb can be placed immediately above or below the address (with some clearance), or near the bottom-right of the mailpiece. USPS offers some more guidance on placement.
I think applying IMb labels (with the delivery point code) to postcards helps save space and allows you to write over the barcode clear zone (where USPS would print their own IMb, based on the OCRed address). I’ve noticed postcards without white space left for the clear zone are generally still delivered but take longer.
In my experience, USPS doesn’t apply their own IMb to mailpieces that already have an IMb with the delivery point information. They might still print fluorescent barcodes on the back.
IMb Tracking
After you’ve started adding IMb codes to your letters, their tracking will begin to update! For mail deposited before the collection time in USPS blue boxes or at a Post Office (excluding hand-cancelled items submitted at the service counter), there will generally be a “Cancellation of Postage” scan the night of the day it’s collected.
- Log into iv.usps.com.
- Under the “View Data” tab (pre-selected), click
- “+ ADD ALL CRIDs” in the first box
- “+ ADD ALL MIDs” in the second box
- “NEXT STEP” at the bottom-right
- On the next screen, under “Prepare for Data Download, “click “USE THIS METHOD.”9
- From the drop-down menu under “Mail Object Type,” select “Piece.”
- Fill out the date range you’d like under “Required Filter.”
- Under “Data Fields,” you can click “Add All” so that you can decide which you’d actually like to use next time (not all of them will be populated). I’ve settled on “IMb Serial,” “Scan DateTime,” “Scan Facility ZIP,” “Scan Event Code,” and “Mail Phase.”
- If you’re interested in more information on the tracking events, you can find it in this Excel sheet.
- Once you settle on a configuration, you can save it using the “SAVE VIEW” button. After clicking, make sure to select “Save As” at the top. This step is required if you actually want your configuration to save, rather than just pretend to.
- In the bottom-right, click “FINISH.”
- Click “CONFIRM” in the bottom-right.
- If you want to make changes, click “UPDATE,” not “CANCEL.” The latter will reset the process to “step 2” above.
- Wait a little bit, then, under the “One-Time Query Output History” section at the bottom, click the dog-eared-paper icon under the “ACTION” column. If it says no files are available, wait a little longer, and refresh the page. There will be an alert at the top once the file is ready for download.
- Once you’ve downloaded the file, open it in Excel or similar.
- I like Google Sheets for this because it’s less annoying about the fields’ data types (e.g., it doesn’t convert the IMb code to scientific notation by default).
- I just look through the scans by hand, but you could process them further if you’d like.
There is an IMb scanner app by Ashwood Data on iOS. It scans and surfaces tracking information for traceable IMb codes in a pleasant interface. It’s not without its issues (it harasses users about signing up for an account; it seems like it’s limited to displaying four tracking events max; the scanner interface is finicky; you must scan the IMb codes and cannot enter them manually), but it’s free and worth a try. You can use it to scan the IMb codes on marketing (and other commercial) mail you receive, which is a fun bonus.
That’s All!
Thanks for reading! I hope this guide has been useful to you. I enjoy checking my aggregate reports every few days and reconciling the tracking events against my spreadsheet of sent mail.
Relatedly, I’ve used Informed Delivery, the USPS service that emails you pictures of the front of your envelopes the morning of the day they arrive in your mailbox, for almost six years. It’s easily my most-opened email type, save for personal correspondence, and is probably based on the technology behind Informed Visibility (IV). They’ve even begun sending mail delivery notifications, which are generated, like the delivery events on IV, by the mail truck driving past your address. It’s worth checking out if you haven’t already.
Let me know what you think by sending me an email, and subscribe to my email list if you’d like to hear more from me.
- I send a lot of these! ↩︎
- Because letters aren’t scanned upon delivery, the “delivered” event is assumed based on the mail truck, presumably carrying the letter in question, having driven by the delivery address. ↩︎
- Yes, it’s redundant to say “Intelligent Mail barcode codes.” I like this better than writing “IMb’s” because the apostrophe looks wrong but is necessary to distinguish the lowercase “s” from the lowercase “b.” ↩︎
- This depends on the length of your mailer ID and other factors (USPS will generate their own IMb codes, for example), but your mailer ID will probably be nine digits like mine. ↩︎
- I originally thought this meant you needed a USPS account manager. You don’t. ↩︎
- This might be obvious, though that number appears three times on the “Mailer ID” page, while the mailer ID appears once. Helpfully, the number above the business address is 8 digits and cannot be a mailer ID (not 6 or 9). ↩︎
- “Nonautomation” doesn’t mean it’s not processed through automated mail equipment; it has something to do with how a large mailer would prepare mailpieces for USPS. ↩︎
- USPS is reminding me of IB with how much they like initialisms. ↩︎
- “Prepare for Online View” doesn’t surface information on individual mailpieces. I found out about this from this comment. ↩︎