Quick answer: fill in the five fields – Barcode Identifier (usually 00), Service Type ID, your USPS Mailer ID, a serial number and the delivery ZIP code (5, 9 or 11 digits) – and press “Use these fields”. The 65-bar barcode is drawn at the official size for printing above the address.
The five parts of an IMb
| Field | Digits | Notes |
|---|---|---|
| Barcode Identifier | 2 | Normally 00; the second digit must be 0–4 |
| Service Type ID (STID) | 3 | Mail class plus services such as tracking or address correction – taken from the USPS STID table |
| Mailer ID | 6 or 9 | Identifies the mail owner or service provider |
| Serial number | 9 or 6 | Must make the piece unique for 45 days to get full-service prices |
| Routing code | 0, 5, 9 or 11 | Delivery ZIP, ZIP+4 or ZIP+4+delivery point |
The Mailer ID and serial number always add up to 15 digits: a 6-digit Mailer ID pairs with a 9-digit serial, a 9-digit Mailer ID with a 6-digit serial.
How to create a USPS Intelligent Mail barcode
- Get your Mailer ID. Mailer IDs are issued free through the USPS Business Customer Gateway.
- Fill in the fields. Barcode ID, Service Type ID for your mail class and services, Mailer ID, serial number and routing ZIP.
- Use the fields. The 20-digit tracking code and routing code are joined into the barcode data.
- Print it. Place the barcode in the address block. For a whole mailing, use the bulk option with one 20–31 digit code per line.
Four states, 65 bars
Each bar has one of four shapes: full height, ascender (top half plus middle), descender (middle plus bottom half) or tracker (middle only). The 31 digits plus an 11-bit CRC are converted into these 65 bars, which is why the barcode looks like a row of uneven teeth. USPS replaced the older POSTNET and PLANET barcodes with the IMb in January 2013 for automation prices.
Printing tips
- The barcode is about 2.7–3.2 inches long and 0.125–0.165 inch tall; keep it at 100 %.
- Leave a clear zone of at least 1/8 inch (3.2 mm) on the left and right and keep printing and window edges clear of the bars above and below.
- Print in black on white or light envelopes; check that window envelopes show the whole barcode.
Frequently asked questions
Where do I get a Mailer ID?
From USPS through the Business Customer Gateway. Mailers sending large volumes get 6-digit IDs, others 9-digit IDs.
Which Service Type ID should I use?
It depends on the mail class (First-Class, Marketing Mail, Periodicals) and the services you want, such as tracking or electronic address correction. USPS publishes the list of STIDs.
Can I still print POSTNET?
POSTNET is retired for automation prices but some older systems still read it. You can make it on our Postal Barcode Generator page.
Why is my serial number padded with zeros?
The Mailer ID and serial number must total 15 digits, so shorter serial numbers are filled with leading zeros.
Can I make IMb barcodes for a whole mailing?
Yes. Prepare one complete 20–31 digit code per line and use the bulk option to get a ZIP or a printable sheet.