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Intelligent Mail Barcode (IMb) Standards & Application Flashcards

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  1. What does the abbreviation 'IMb' stand for in USPS postal operations?

    Answer: Intelligent Mail barcode

    IMb stands for Intelligent Mail barcode, the USPS standard barcode that replaced the legacy POSTNET and PLANET barcodes.

  2. How many bars does a complete Intelligent Mail barcode contain?

    Answer: 65

    A complete IMb contains exactly 65 bars, each of which can be in one of four states: tracker, ascender, descender, or full.

  3. Which legacy USPS barcodes did the Intelligent Mail barcode replace?

    Answer: POSTNET and PLANET

    The IMb was designed to replace and consolidate the older POSTNET (routing) and PLANET (tracking) barcodes into a single, more capable barcode.

  4. What is the Service Type Identifier (STID) component of the IMb?

    Answer: A 3-digit code identifying mail class and special services requested

    The STID is a 3-digit code within the IMb that identifies the class of mail and any special services (such as ACS or return services) requested by the mailer.

  5. How many digits can a USPS-assigned Mailer ID (MID) contain in the Intelligent Mail barcode?

    Answer: 6 or 9 digits

    USPS assigns Mailer IDs in two lengths — 6 digits or 9 digits — which determines the paired Serial Number length so that both fields together always total 15 digits.

  6. What is the maximum number of digits in the Routing Code field of the Intelligent Mail barcode?

    Answer: 11 digits (ZIP+4 plus delivery point)

    The Routing Code can contain 0, 5, 9, or 11 digits; at 11 digits it encodes the 5-digit ZIP, the 4-digit add-on, and the 2-digit delivery point — providing the most precise routing information.

  7. Which of the following best describes the Full-Service Intelligent Mail barcode option?

    Answer: A program offering additional postage discounts in exchange for unique barcodes and electronic documentation submission

    Full-Service IMb is a USPS program that offers additional postage discounts to mailers who use unique barcodes per mailpiece and submit postage statements and container data electronically.

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Sources & references

Exam facts on this page (fees, format, dates, passing scores) are checked against these official sources; the date is our last check. Editorial policy

  1. postalpro.usps.com — Test delivery, eligibility, exam format, renewal, score validity, passing score, score release · verified Oct 2026
  2. pe.usps.com — Fees · verified Oct 2026