Understanding the IMB

Decode the Barcode!

Ever wonder what all the lines mean in an Intelligent Mail Barcode (IMB)? Follow along to understand what an Intelligent Mail Barcode is and what all the lines mean!

The Intelligent Mail Barcode combines the data of the existing POSTNET™ and the PLANET Code® barcodes. It also has other data going into that single barcode being generated. The IMB consists of four different vertical bar types going off the different heights of the bar. The four types of bars are: Ascender, Full, Tracker, and Descender as shown below.

Now for the data in the IMB!

The IMB is a maximum of 31-characters in a data string. This converts into 65 bars of the above different heights. The 31-character data string contains a maximum 11-character routing code and a 20-chatacter tracking code (the first four fields).

  1. The Barcode Identifier: 2-didgit field that states the level of presort qualification for that specific mail piece.
  2. The Service Type Identifier (STID): 3-digit field representing the class of mail, intelligent mail option and any addition services requested, if any.
  3. The Mail Identifier: 6 or 9-digit number the USPS assigns that identifies a specific agent in the mailing supply chain. Mail preparers and owners are assigned this 6 or 9-digit number based on their annual mail volume as verified by the USPS.
  4. The Serial Number: This is a 6 to 9-digit filed and the length depends on the Mailer ID. Depending on the type of mail there are different rules for the serial number. For example, if the mail piece is a basic option mailing the serial number does not have any requirements for uniqueness. If it is qualified for Full-Service mailing then the number must be unique within that set and be kept that way for 45 days from the postage statement of the mailing date.
  5. The Routing Code: This field is basically the same information as the POSTNET barcode. It can contain no data, the 5-digit ZIP code data, the 9-digit ZIP + 4-digit code data, or the 11-digit delivery point barcode data.

See the figures below to break it down more visually.

Type Field Digits
Tracking Code Barcode Identifier 2 (2nd digit must be 0–4)
Service Type Identifier 3
Mailer Identifier 6 or 9
Serial Number 9 (when used with 6 digit Mailer ID)6 (when used with 9 digit Mailer ID)
Routing Code Delivery Point ZIP Code 0, 5, 9, or 11
Total 31 maximum

The Finished Piece!

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