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Intelligent Mail barcodes on letters, flats and trays

The Intelligent Mail barcode on a letter or flat encodes up to 31 digits in 65 bars: a 20-digit tracking code and a ZIP Code. Trays, tubs and sacks carry an Intelligent Mail tray label with a 24-digit barcode, and pallets a 21-character Intelligent Mail container barcode. All three carry the mailer's Mailer ID.

Updated November 5, 202674 sources

Questions

How do you read a USPS Intelligent Mail barcode?

An Intelligent Mail barcode's 65 bars hold a 20-digit tracking code, for the mailer, service and serial number, and a routing code, for the delivery point ZIP Code. When its human-readable line is printed, a space separates the fields, as in 01 234 567094 987654321 01234 5678 91. USPS's free online encoder/decoder turns the bars back into digits.

What does an Intelligent Mail barcode look like?

It is a row of 65 bars of four kinds, full bars, ascenders, descenders and trackers, between 0.125 and 0.165 inch tall. The bars are printed 22 to the inch, give or take 2, at least 2.667 inches from the first bar to the last and no more than 3.225 inches overall. The encoder gives the bars as a string of 65 letters, F for a full bar, A an ascender, D a descender and T a tracker: tracking code 00040123456200800001 with routing code 987654321 is ADTTTATTTFTDFADTDTFTAATATADDDDFTTDTDFFDFTTATAFFDDADDTFFADFDFTTTAD.

What is an Intelligent Mail barcode?

The Intelligent Mail barcode, or IMb, is a 65-bar USPS barcode used to sort and track letters and flats. It can combine the data of the older POSTNET and PLANET Code barcodes, and other data, in one barcode. Since January 28, 2013, when USPS ended price eligibility for POSTNET barcodes, letters and flats need it to qualify for automation prices.

Where can I download an Intelligent Mail barcode font for free?

USPS offers Intelligent Mail barcode fonts and encoder software for download from PostalPro, at no charge. The fonts come for five production printing environments, TrueType among them. The barcode's human-readable line, when required, is printed in a sans serif font, at a minimum of 10- to 12-point type. USPS licenses its encoder software and fonts for use in the mailing industry without a royalty or other fee.

How do you create an Intelligent Mail barcode?

A mailer joins the barcode's five fields into a 20- to 31-digit string, encodes it into 65 characters, and prints those with the Intelligent Mail barcode font. The mailer needs a Mailer ID from USPS first. Small business mailers can use Intelligent Mail for Small Business Mailers, a free online tool that makes the barcodes for pieces and tray labels.

How do you decode an Intelligent Mail barcode?

USPS's free online encoder/decoder turns an Intelligent Mail barcode's bars into its tracking code and delivery point ZIP Code, or back. Unlike POSTNET, where each digit is a fixed pattern of five bars, the bars come from an encoding algorithm in Specification USPS-B-3200.

Where does the Intelligent Mail barcode go on a letter or flat?

On a letter, the Intelligent Mail barcode goes in the address block or in the barcode clear zone in the lower right corner. On a flat, it can go anywhere on the address side at least 1/8 inch from every edge. Only one Intelligent Mail barcode can go in the same area.

Can an Intelligent Mail barcode have fewer than 65 bars?

No: an Intelligent Mail barcode always has 65 bars, whatever the length of the ZIP Code in it. The ZIP Code's length changes only the string the encoder takes, from 20 to 31 digits. A POSTNET barcode, by contrast, had 32 bars for a 5-digit ZIP Code and 62 bars for an 11-digit delivery point code.

How can I check that my Intelligent Mail barcodes are generated correctly?

USPS suggests a handheld scanner, or the local USPS Mailpiece Design Analyst, to check that Intelligent Mail barcodes are generated correctly. Mailers and USPS must both inspect and test printed Intelligent Mail barcodes as a routine.

How it fits together

Barcodes go on single mailpieces and on the labels of the trays, sacks and pallets that carry them. Mailers print an Intelligent Mail barcode, or IMb, on each letter or flat, and USPS uses it to sort and track the piece. Its Service Type Identifier marks the piece as Full-Service or basic and sets how USPS handles it if undeliverable. Full-Service is an Intelligent Mail option that requires unique piece barcodes, barcoded tray and container labels, and electronic documentation. Mailers make the barcode with encoder software and fonts that USPS gives away.

The pieces travel in trays, tubs and sacks, each with an Intelligent Mail tray label whose 24-digit barcode identifies that unit. Trays and sacks go on pallets and similar containers, each labeled with an Intelligent Mail container barcode. All three barcodes carry a Mailer ID, a number USPS assigns to identify the mail owner or mail preparer. USPS assigns Mailer IDs generally through the Business Customer Gateway, the USPS website that is the single entry point to its online business services.

In a Full-Service mailing, every piece, tray and container needs a barcode that stays unique for 45 days. IMb Tracing, once the source of piece and bundle tracking data, is a retired system. Mail tracking for pieces, bundles, trays and containers is consolidated into Informed Visibility Mail Tracking & Reporting, which tracks them in near real time. Parcels carry a barcode similar in purpose, the Intelligent Mail package barcode of package labels.

Before the IMb, a POSTNET barcode carried the ZIP Code and a PLANET Code tracked the piece. The IMb replaced both. USPS also defines formats of the IMb for its own use. A separate mark, the Facing Identification Mark, helps machines orient and separate certain types of mail. A clear zone around the IMb lets barcode readers find and read it.

The barcode on letters and flats

The IMb's 20-digit tracking code identifies and tracks the piece, and its routing code holds the Delivery Point ZIP Code that routes it. The routing code holds 0, 5, 9 or 11 digits, so the whole string runs from 20 to 31 digits. The tracking code holds four fields, in this order:

  • The Barcode Identifier, 2 digits: 00 unless an automation-price flat carries an optional endorsement line. That line, printed on top of the address block, shows the sort level of the piece's bundle, and the Barcode Identifier then encodes it.
  • The Service Type Identifier, or STID, 3 digits, for the mail class and the services requested.
  • The Mailer ID, 6 or 9 digits, which USPS assigns.
  • The serial number, set by the mailer: 9 or 6 digits, so that it and the Mailer ID make 15.

A unique IMb differs from piece to piece, and a static IMb is the same on every piece. Full-Service mailpieces must have a unique IMb, and basic automation mailpieces need not. The Mailer ID, the serial number and the mail class in the STID make an IMb unique. In Full-Service mailings, the 15-digit pair of Mailer ID and serial number can't repeat within a class for 45 days.

The STID Table on PostalPro gives the STID to use for each combination of services. Those services include Full-Service or basic, and the use of Informed Visibility Mail Tracking & Reporting, or IV-MTR.

The four First-Class Mail STIDs with no address correction, one for each service level and IV-MTR choice.

Service Type IDentifier (STID) Table, effective January 21, 2024
STIDMail classOptionService levelInformed Visibility Mail Tracking & Reporting
300First-Class Mail®No Address Corrections – No Printed EndorsementsBasic or NonautomationWithout IV® MTR
310First-Class Mail®No Address Corrections – No Printed EndorsementsBasic or NonautomationWith IV® MTR
260First-Class Mail®No Address Corrections – No Printed EndorsementsFull-ServiceWithout IV® MTR
270First-Class Mail®No Address Corrections – No Printed EndorsementsFull-ServiceWith IV® MTR

4 codes in the Service Type IDentifier (STID) Table, effective January 21, 2024, where STID is 300 or 310 or 260 or 270.

Barcode Identifier

Also called BI

“The BI is a specific two-digit identifier assigned by the Postal Service primarily to encode the presort identification that is printed in human readable form on the optional endorsement line (OEL) as well as a Mailer or Postal source channel identifier.”

Serial Number

Also called SN

“The portion of the Intelligent Mail barcode that identifies a single piece of mail.”

Routing Code

“The portion of the Intelligent Mail barcode that contains the ZIP Code for the address on the mail piece.”

unique IMb

“a barcode that does vary by mailpiece”

static IMb

“a barcode that does not vary by mailpiece”

Service Type IDentifier (STID) Table

Also called STID Table

“The STID Table located on the PostalPro® website allows you to determine which STID to use based on the mail class, address correction option, use of Informed Visibility – Mail Tracking & Reporting (IV®-MTR), and whether the mail contains a Full Service or Basic IMb.”

tracking code

“Part of the Intelligent Mail barcode that consists of 20 digits containing the Barcode Identifier, the Service Type Identifier, Mailer Identifier (MID), and Serial Number.”

Service Type Identifiers

Also called STID, STIDS, STI, Service Type IDs, Service Type ID(s)

“A unique three-digit code embedded in the Intelligent Mail® barcode (IMb®) that indicates the service type for an individual mailpiece.”

Encoders, fonts and the decoder

An encoder turns the IMb's digits into a 65-character string, and a special font prints that string as the bars. The encoder takes a 20-digit tracking code and a routing code of none, 5, 9 or 11 digits. It returns 65 letters, one for each bar, each naming the bar's type.

LetterBar
FFull bar
AAscender
DDescender
TTracker

Specification USPS-B-3200 defines the algorithm that turns the 31 digits into 65 bars. The data fields carry no checksum: the encoding adds error detection and correction itself.

USPS supports its encoder software in 24 combinations of programming language and platform. Each package is a standard ZIP file with a user guide inside. The online encoder/decoder does the same conversion in either direction. Intelligent Mail for Small Business Mailers needs no software either: it runs in a web browser.

4-state barcode

“consists of four types of bars (the four states)”

Intelligent Mail Barcode 4-State Specification

Also called USPS-B-3200

“This document provides the specifications for generating and printing the Intelligent Mail® barcode (IMb) used in the U.S. Postal Service (USPS) mailstream.”

Online Encoder/Decoder

Also called IMb Decoder/Encoder, Barcode Decoder/Encoder

“Use this online tool to quickly Decode (convert a sequence of bars into meaningful tracking and delivery point ZIP information) or Encode (generate a barcode based on tracking and delivery point ZIP information) the Intelligent Mail barcode.”

full bar

“(1) In POSTNET barcode symbology, the tall bar that covers both the invisible top and bottom regions. (2) In Intelligent Mail barcode symbology, the longest bar that covers all three regions (from bottom to top): the descending (bottom) region, tracking (middle) region, and ascending (top) region.”

ascender

“In Intelligent Mail barcode symbology, the bar that covers two of the three possible regions (from bottom to top): the tracking (middle) region and ascending (top) region. It does not cover the descending (bottom) region.”

descender

“In Intelligent Mail barcode symbology, the bar that covers two of the three possible regions (from bottom to top): the descending (bottom) region and tracking (middle) region. It does not cover the ascending (top) region.”

tracker

“In Intelligent Mail barcode symbology, the bar that covers only one of the three possible regions (from bottom to top): the tracking (middle). It does not cover the descending (bottom) region and ascending (top) region.”

Intelligent Mail Barcode (IMb) Encoder Software and Fonts

“The Postal Service provides Intelligent Mail® barcode files, fonts and encoders, available for download.”

Tray and container barcodes

Each tray, sack and pallet of mail has a label whose barcode describes the mail inside, its origin and its destination. The tray barcode identifies one tray, tub or sack and the mailer who prepared it. The container barcode identifies one pallet or similar container and its mail owner, and links it to the mailing's electronic record.

IMbTray barcodeContainer barcode
Goes onLetters and flatsTrays, tubs and sacksPallets and similar containers
DataUp to 31 digits24 digits21 characters
Symbology65 bars in 4 statesISS Code 128GS1-128 or GS1 DataMatrix
Unique byMailer ID, serial number and mail classAll 24 digitsAll 21 characters

Besides the Mailer ID and a serial number, the tray barcode holds the unit's destination ZIP Code and a code for its contents. A 5-digit presort tray carries its 5-digit ZIP Code, and a 3-digit tray its 3-digit ZIP Code followed by two zeros. The contents code is a 3-digit Content Identifier Number from the Domestic Mail Manual.

Every tray and sack in a presorted mailing must carry an Intelligent Mail tray label. Automation-price letter and flat mailings must use barcoded tray labels. Using the label does not by itself meet the Full-Service requirements. Full-Service goes further and needs every label's barcode to be unique.

Must
Full-Service requires a unique IMtb on each handling unit label when mail is prepared using trays or sacks, and a unique IMcb on each container label when mail is placed on pallets or other containers. These barcodes must remain unique for a 45-day period.

A Full-Service mailing must give every tray, sack and container label its own barcode. Each of those barcodes must stay unique for 45 days.

In Mail.XML files for eInduction, every container barcode must begin with 99M and be 21 characters long.

Content Identifier Number

Also called CIN, Content Identification Number

“The applicable 3-Digit CIN that correctly describes the contents of the tray or sack based on the Mailer CIN List in the DMM.”

Destination ZIP Code

“the 3 or 5-digit ZIP Code for the tray or sack’s destination, or the ZIP Code of the mail within the container”

Intelligent Mail container barcode

Also called IMcb

“Container barcode is used on mailer-generated pallet labels to uniquely identify pallets and similar containers (i.e., all-purpose containers, hampers, pallet boxes, etc.)”

Other barcodes and marks

POSTNET is a legacy barcode of full and half bars that carries a ZIP Code, ZIP+4 code or delivery point code. Its bars, in groups of five, stand for the digits, plus a correction digit. A POSTNET barcode with the nine digits of the ZIP+4 code plus two more is a delivery point barcode. The IMb's routing code can carry the same delivery point code.

The PLANET Code, a second legacy barcode of long and short bars, tracked mail electronically. Since January 28, 2013, automation prices need an IMb, and a POSTNET barcode is not eligible for them.

USPS applies IMbs of its own, marked by Barcode Identifier values reserved for USPS. A Postal Intelligent Mail barcode uses the STID, Mailer ID and serial number fields for USPS letter ID tag data. A Redirection Intelligent Mail barcode marks a piece that had a mailer's IMb and was redirected from its original destination. A redirected piece with no mailer IMb gets a Postal Intelligent Mail barcode instead. On flats, USPS's Flat Mail Identification Code Sort program applies a look-alike 4-state barcode as an ID tag, only to flats with no barcode.

The Facing Identification Mark, or FIM, is a pattern of bars that helps a facer-canceler identify, orient and separate certain mail. It is printed along the top edge of a letter or card, left of the postage. It marks types such as Business Reply Mail and PC Postage mail. Different bar combinations mark different types of mail, such as FIM E on Share Mail, part of reply mail.

Postal Numeric Encoding Technique

Also called POSTNET

“The POSTNET barcode is a legacy barcode used by the Postal Service for translating ZIP Code, ZIP+4 code, and delivery point code information into a machine-readable format that consists of a series of vertical full and half bars.”

Delivery Point Barcode

Also called DPBC

“A general term for a POSTNET barcode that contains the nine digits of the ZIP+4 code plus two digits, which are generally the last two digits of the primary street address number (or Post Office Box, etc.).”

Postal Alphanumeric Encoding Technique

Also called PLANET, PLANET Code - Legacy, PLANET Code

“The PLANET Code is a legacy 12-digit (long and short bars) barcode used to track mail electronically.”

Postal Intelligent Mail barcode

Also called pIMb, Postal IMb

“A USPS-applied pIMb is identified by the Barcode ID value of 94 and indicates that the pIMb barcode is constructed differently from the Mailer IMb.”

Redirection Intelligent Mail barcode

Also called rIMb, Redirection IMb

“The BI value of 93 identifies a Redirection IMb (rIMb) and indicates that the mailpiece originally contained a mailer-applied IMb and has been redirected from its original destination.”

Facing Identification Mark

Also called FIM

“A pattern of vertical bars and spaces used by automated postal equipment such as a facercanceler to identify, orient, and separate certain types of mail.”

Print quality

A clear zone, a margin kept clear around the IMb, lets barcode readers find and read it. It is at least 0.028 inch over and under the barcode and 0.125 inch at each end. On letters, the barcode clear zone is a separate area: a rectangle in the lower right corner kept free of other printing.

The IMb itself is 0.125 to 0.165 inch tall, at 22 bars per inch, give or take 2. Its background must reflect at least 50 percent of red light and 45 percent of green light. The print reflectance difference between the bars and the background must be at least 30 percent. Other printing in the clear zone, insert show-through included, must stay at or under a print contrast ratio of 15 percent.

Every tray label barcode in a mailing must measure American National Standards Institute grade A, B or C. At least 70 percent must measure grade A or B.

A container barcode's darkest bar must reflect at most half as much light as its lightest space. Its symbol contrast must exceed 40 percent. A GS1-128 container barcode's X-dimension, the width of its narrowest bar or space, must be 0.0225 to 0.0275 inch. A GS1 DataMatrix container barcode has an X-dimension rule of its own. Tray labels and container labels both need a printer of at least 203 dots per inch.

Reflectance Maximum

Also called R max

“Highest reflectance value, normally the reflectance value of the lightest space within the barcode symbol, including the quiet zones.”

Reflectance Minimum

Also called R min

“Lowest reflectance value, normally the reflectance value of the darkest bar within the barcode symbol, including the quiet zones.”

Print Reflectance Difference

Also called PRD

“The print reflectance difference (PRD) shall be the difference between light reflected from the printed barcode and the background when measured with a Postal Service envelope reflectance meter or equivalent.”

Symbol Contrast

Also called SC

“Difference between the highest reflectance value and the lowest reflectance value anywhere in the scan reflectance profile, including the quiet zones.”

X-dimension

“The nominal width of the narrowest bar or space element within the barcode symbol is defined as the X-dimension.”

Quiet Zone

Also called clear zone

“A clear space with no encoded information that precedes the Start Character of a barcode and follows the Stop Character. Formerly referred to as “Clear Area” or “Light Margin.””

What goes wrong

  • In Full-Service, a bundle, tray or container whose barcode is not unique gets no feedback.
  • Two pieces of the same mail class with the same Mailer ID and serial number are flagged as non-unique, even when their STIDs differ.
  • In eInduction, a container barcode used on two or more containers within 45 days of the postage statement's mailing date logs a Duplicate error.
  • Common errors that interfere with Address Change Service are a missing or wrong Mailer ID, an STID not requesting it, and an all-zero serial number.
  • A routing code must never be padded with zeros, spaces or nulls that are not part of the ZIP Code.
  • On a letter with two IMbs, the one in the lower right corner generally takes precedence over the one in the address block.
  • Change Service Requested and Return Service Requested are endorsements a sender prints to tell USPS how to handle undeliverable mail. USPS can discard First-Class Mail only when it can make an Address Change Service notice for it. If an undeliverable piece endorsed Change Service Requested has an unreadable IMb, USPS may treat it as endorsed Return Service Requested and return it.
  • Perforations through a tray label's barcode or its clear zones are not permitted.

Index: 34 entries

Service (1)

Systems (2)

Identifiers (19)

Documents (2)

Terms (10)

Sources