# Intelligent Mail barcodes on letters, flats and trays

The [Intelligent Mail barcode](https://postalref.com/products/intelligent-mail-barcode.md) on a letter or flat encodes up to 31 digits in 65 bars: a 20-digit tracking code and a ZIP Code.[^1][^2] Trays, tubs and sacks carry an [Intelligent Mail tray label](https://postalref.com/products/intelligent-mail-tray-label.md) with a 24-digit barcode, and pallets a 21-character Intelligent Mail container barcode.[^3][^4] All three carry the mailer's Mailer ID.[^5]

Updated November 5, 2026. 74 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.[^6] When its human-readable line is printed, a space separates the fields, as in `01 234 567094 987654321 01234 5678 91`.[^7][^8] USPS's free [online encoder/decoder](#encoding) turns the bars back into digits.[^9][^10]

### 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.[^11][^10] 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.[^11] 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`.[^10]

### 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.[^12] It can combine the data of the older POSTNET and PLANET Code barcodes, and other data, in one barcode.[^6] Since January 28, 2013, when USPS ended price eligibility for POSTNET barcodes, letters and flats need it to qualify for automation prices.[^13][^12]

### 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.[^14][^10] The fonts come for five production printing environments, TrueType among them.[^14] The barcode's human-readable line, when required, is printed in a sans serif font, at a minimum of 10- to 12-point type.[^7][^8] USPS licenses its [encoder software and fonts](https://postalref.com/products/intelligent-mail-barcode.md#encoder-software-and-fonts) for use in the mailing industry without a royalty or other fee.[^14]

### 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.[^15] The mailer needs a Mailer ID from USPS first.[^2][^16] Small business mailers can use [Intelligent Mail for Small Business Mailers](https://postalref.com/products/intelligent-mail-barcode.md#imsb), a free online tool that makes the barcodes for pieces and tray labels.[^17]

### 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.[^9][^10] Unlike POSTNET, where each digit is a fixed pattern of five bars, the bars come from an encoding algorithm in Specification USPS-B-3200.[^10]

### 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](https://postalref.com/guides/mailpiece-design.md) in the lower right corner.[^11] On a flat, it can go anywhere on the address side at least 1/8 inch from every edge.[^11] Only one Intelligent Mail barcode can go in the same area.[^18]

### 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.[^19] The ZIP Code's length changes only the string the encoder takes, from 20 to 31 digits.[^20][^15] A POSTNET barcode, by contrast, had 32 bars for a 5-digit ZIP Code and 62 bars for an 11-digit delivery point code.[^21]

### 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.[^22] Mailers and USPS must both inspect and test printed Intelligent Mail barcodes as a routine.[^8]

## How it fits together

Barcodes go on single mailpieces and on the labels of the trays, sacks and pallets that carry them.[^23] Mailers print an [Intelligent Mail barcode](https://postalref.com/products/intelligent-mail-barcode.md), or IMb, on each letter or flat, and USPS uses it to sort and track the piece.[^1][^12] Its [Service Type Identifier](https://postalref.com/products/stids.md) marks the piece as Full-Service or basic and sets how USPS handles it if undeliverable.[^24] [Full-Service](https://postalref.com/guides/full-service.md) is an Intelligent Mail option that requires unique piece barcodes, barcoded tray and container labels, and electronic documentation.[^25] Mailers make the barcode with encoder software and fonts that USPS gives away.[^10]

The pieces travel in trays, tubs and sacks, each with an Intelligent Mail tray label whose 24-digit barcode identifies that unit.[^3] Trays and sacks go on pallets and similar containers, each labeled with an [Intelligent Mail container barcode](https://postalref.com/products/intelligent-mail-container-barcode.md).[^23][^4] All three barcodes carry a [Mailer ID](https://postalref.com/products/mid.md), a number USPS assigns to identify the mail owner or mail preparer.[^5][^16] USPS assigns Mailer IDs generally through the [Business Customer Gateway](https://postalref.com/products/business-customer-gateway.md), the USPS website that is the single entry point to its online business services.[^2][^26]

In a Full-Service mailing, every piece, tray and container needs a barcode that stays unique for 45 days.[^27] IMb Tracing, once the source of piece and bundle tracking data, is a retired system.[^28][^29] [Mail tracking](https://postalref.com/guides/mail-visibility.md) for pieces, bundles, trays and containers is consolidated into Informed Visibility Mail Tracking & Reporting, which tracks them in near real time.[^28] Parcels carry a barcode similar in purpose, the Intelligent Mail package barcode of [package labels](https://postalref.com/guides/package-labels.md).[^6]

Before the IMb, a POSTNET barcode carried the ZIP Code and a PLANET Code tracked the piece.[^30] The IMb replaced both.[^30] USPS also defines formats of the IMb for its own use.[^1] A separate mark, the Facing Identification Mark, helps machines orient and separate certain types of mail.[^31] A clear zone around the IMb lets barcode readers find and read it.[^32]

## 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](https://postalref.com/guides/address-matching.md) that routes it.[^33][^34] The routing code holds 0, 5, 9 or 11 digits, so the whole string runs from 20 to 31 digits.[^20][^15] The tracking code holds four fields, in this order:[^2]

- The Barcode Identifier, 2 digits: `00` unless an automation-price flat carries an optional endorsement line.[^35] 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.[^36][^16][^35]
- The Service Type Identifier, or STID, 3 digits, for the mail class and the services requested.[^16]
- The Mailer ID, 6 or 9 digits, which USPS assigns.[^16]
- The serial number, set by the mailer: 9 or 6 digits, so that it and the Mailer ID make 15.[^16][^15][^37]

A unique IMb differs from piece to piece, and a static IMb is the same on every piece.[^38] Full-Service mailpieces must have a unique IMb, and basic automation mailpieces need not.[^37] The Mailer ID, the serial number and the mail class in the STID make an IMb unique.[^37] In Full-Service mailings, the 15-digit pair of Mailer ID and serial number can't repeat within a class for 45 days.[^37]

The STID Table on PostalPro gives the STID to use for each combination of services.[^39] Those services include Full-Service or basic, and the use of [Informed Visibility Mail Tracking & Reporting](https://postalref.com/products/iv-mtr.md), or IV-MTR.[^39]

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

| STID | Mail class | Option | Service level | Informed Visibility Mail Tracking & Reporting |
| --- | --- | --- | --- | --- |
| `300` | First-Class Mail® | No Address Corrections – No Printed Endorsements | Basic or Nonautomation | Without IV® MTR |
| `310` | First-Class Mail® | No Address Corrections – No Printed Endorsements | Basic or Nonautomation | With IV® MTR |
| `260` | First-Class Mail® | No Address Corrections – No Printed Endorsements | Full-Service | Without IV® MTR |
| `270` | First-Class Mail® | No Address Corrections – No Printed Endorsements | Full-Service | With 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.”[^20]
- **Serial Number**, also called SN: “The portion of the Intelligent Mail barcode that identifies a single piece of mail.”[^40]
- **Routing Code**: “The portion of the Intelligent Mail barcode that contains the ZIP Code for the address on the mail piece.”[^40]
- **unique IMb**: “a barcode that does vary by mailpiece”[^38]
- **static IMb**: “a barcode that does not vary by mailpiece”[^38]
- **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.”[^39]
- **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.”[^41]
- **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.”[^42]

## 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.[^34] The encoder takes a 20-digit tracking code and a routing code of none, 5, 9 or 11 digits.[^10] It returns 65 letters, one for each bar, each naming the bar's type.[^10]

| Letter | Bar |
| --- | --- |
| `F` | Full bar[^10] |
| `A` | Ascender[^10] |
| `D` | Descender[^10] |
| `T` | Tracker[^10] |

Specification USPS-B-3200 defines the algorithm that turns the 31 digits into 65 bars.[^10] The data fields carry no checksum: the encoding adds error detection and correction itself.[^20]

USPS supports its encoder software in 24 combinations of programming language and platform.[^14] Each package is a standard ZIP file with a user guide inside.[^10] The online encoder/decoder does the same conversion in either direction.[^9][^10] Intelligent Mail for Small Business Mailers needs no software either: it runs in a web browser.[^17]

- **4-state barcode**: “consists of four types of bars (the four states)”[^1]
- **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.”[^1]
- **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.”[^9]
- **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.”[^25]
- **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.”[^43]
- **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.”[^44]
- **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.”[^41]
- **Intelligent Mail Barcode (IMb) Encoder Software and Fonts**: “The Postal Service provides Intelligent Mail® barcode files, fonts and encoders, available for download.”[^14]

## 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.[^23] The tray barcode identifies one tray, tub or sack and the mailer who prepared it.[^45] The container barcode identifies one pallet or similar container and its mail owner, and links it to the mailing's electronic record.[^46]

| | IMb | Tray barcode | Container barcode |
| --- | --- | --- | --- |
| Goes on | Letters and flats[^12] | Trays, tubs and sacks[^3] | Pallets and similar containers[^4] |
| Data | Up to 31 digits[^1] | 24 digits[^3] | 21 characters[^4] |
| Symbology | 65 bars in 4 states[^1] | ISS Code 128[^3] | GS1-128 or GS1 DataMatrix[^4] |
| Unique by | Mailer ID, serial number and mail class[^37] | All 24 digits[^37] | All 21 characters[^37] |

Besides the Mailer ID and a serial number, the tray barcode holds the unit's destination ZIP Code and a code for its contents.[^3] A 5-digit [presort](https://postalref.com/guides/presort.md) tray carries its 5-digit ZIP Code, and a 3-digit tray its 3-digit ZIP Code followed by two zeros.[^47] The contents code is a 3-digit Content Identifier Number from the Domestic Mail Manual.[^47]

Every tray and sack in a presorted mailing must carry an Intelligent Mail tray label.[^48] Automation-price letter and flat mailings must use barcoded tray labels.[^49] Using the label does not by itself meet the Full-Service requirements.[^50] Full-Service goes further and needs every label's barcode to be unique.[^37]

> 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.[^37]

**Must.** 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](https://postalref.com/products/einduction.md), every container barcode must begin with `99M` and be 21 characters long.[^51][^4]

- **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.”[^52]
- **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”[^53]
- **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.)”[^46]

## 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.[^30] Its bars, in groups of five, stand for the digits, plus a correction digit.[^21] A POSTNET barcode with the nine digits of the ZIP+4 code plus two more is a delivery point barcode.[^54] The IMb's routing code can carry the same [delivery point code](https://postalref.com/guides/address-matching.md).[^54]

The PLANET Code, a second legacy barcode of long and short bars, tracked mail electronically.[^30] Since January 28, 2013, automation prices need an IMb, and a POSTNET barcode is not eligible for them.[^13][^55]

USPS applies IMbs of its own, marked by Barcode Identifier values reserved for USPS.[^56] A Postal Intelligent Mail barcode uses the STID, Mailer ID and serial number fields for USPS letter ID tag data.[^56] A Redirection Intelligent Mail barcode marks a piece that had a mailer's IMb and was [redirected](https://postalref.com/guides/undeliverable-mail.md) from its original destination.[^57] A redirected piece with no mailer IMb gets a Postal Intelligent Mail barcode instead.[^57] 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.[^58]

The Facing Identification Mark, or FIM, is a pattern of bars that helps a facer-canceler identify, orient and separate certain mail.[^31] It is printed along the top edge of a letter or card, left of the postage.[^31] It marks types such as Business Reply Mail and PC Postage mail.[^31] Different bar combinations mark different types of mail, such as FIM E on Share Mail, part of [reply mail](https://postalref.com/guides/reply-mail.md).[^31][^59]

- **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.”[^30]
- **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.).”[^54]
- **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.”[^30]
- **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.”[^56]
- **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.”[^57]
- **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.”[^31]

## Print quality

A clear zone, a margin kept clear around the IMb, lets barcode readers find and read it.[^32] It is at least 0.028 inch over and under the barcode and 0.125 inch at each end.[^11] On letters, the barcode clear zone is a separate area: a rectangle in the lower right corner kept free of other printing.[^23]

The IMb itself is 0.125 to 0.165 inch tall, at 22 bars per inch, give or take 2.[^11] Its background must reflect at least 50 percent of red light and 45 percent of green light.[^60] The print reflectance difference between the bars and the background must be at least 30 percent.[^60] Other printing in the clear zone, insert show-through included, must stay at or under a print contrast ratio of 15 percent.[^60]

Every tray label barcode in a mailing must measure American National Standards Institute grade A, B or C.[^61] At least 70 percent must measure grade A or B.[^61]

A container barcode's darkest bar must reflect at most half as much light as its lightest space.[^62] Its symbol contrast must exceed 40 percent.[^62] A GS1-128 container barcode's X-dimension, the width of its narrowest bar or space, must be 0.0225 to 0.0275 inch.[^62] A GS1 DataMatrix container barcode has an X-dimension rule of its own.[^63] Tray labels and container labels both need a printer of at least 203 dots per inch.[^64][^62]

- **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.”[^65]
- **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.”[^65]
- **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.”[^60]
- **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.”[^66]
- **X-dimension**: “The nominal width of the narrowest bar or space element within the barcode symbol is defined as the X-dimension.”[^66]
- **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.””[^65]

## What goes wrong

- In [Full-Service](https://postalref.com/guides/full-service.md), a bundle, tray or container whose barcode is not unique gets no feedback.[^67]
- Two pieces of the same mail class with the same Mailer ID and serial number are flagged as [non-unique](https://postalref.com/guides/full-service.md), even when their STIDs differ.[^68]
- In eInduction, a [container barcode](https://postalref.com/products/intelligent-mail-container-barcode.md#problems) used on two or more containers within 45 days of the postage statement's mailing date logs a Duplicate error.[^69]
- Common errors that interfere with [Address Change Service](https://postalref.com/products/stids.md#acs) are a missing or wrong Mailer ID, an STID not requesting it, and an all-zero serial number.[^70]
- A [routing code](https://postalref.com/products/intelligent-mail-barcode.md#rules) must never be padded with zeros, spaces or nulls that are not part of the ZIP Code.[^19]
- On a letter with [two IMbs](https://postalref.com/products/intelligent-mail-barcode.md#placement), the one in the lower right corner generally takes precedence over the one in the address block.[^70]
- Change Service Requested and Return Service Requested are endorsements a sender prints to tell USPS how to handle undeliverable mail.[^71][^72] USPS can discard First-Class Mail only when it can make an Address Change Service notice for it.[^73] If an undeliverable piece endorsed Change Service Requested has an unreadable IMb, USPS may treat it as endorsed Return Service Requested and [return it](https://postalref.com/products/stids.md#problems).[^73]
- Perforations through a [tray label's](https://postalref.com/products/intelligent-mail-tray-label.md#problems) barcode or its clear zones are not permitted.[^74]

## Index: 34 entries

### Service (1)

- [Intelligent Mail Barcode (IMb) Encoder Software and Fonts](https://postalref.com/products/intelligent-mail-barcode.md#encoder-software-and-fonts)

### Systems (2)

- [Customer Label Distribution System](https://postalref.com/products/intelligent-mail-tray-label.md#clds)
- [Online Encoder/Decoder](https://postalref.com/guides/intelligent-mail.md#encoding)

### Identifiers (19)

- [4-state barcode](https://postalref.com/guides/intelligent-mail.md#encoding)
- [Barcode Identifier](https://postalref.com/guides/intelligent-mail.md#imb)
- [Content Identifier Number](https://postalref.com/guides/intelligent-mail.md#trays-containers)
- [Delivery Point Barcode](https://postalref.com/guides/intelligent-mail.md#other-barcodes)
- [Destination ZIP Code](https://postalref.com/guides/intelligent-mail.md#trays-containers)
- [Facing Identification Mark](https://postalref.com/guides/intelligent-mail.md#other-barcodes)
- [Intelligent Mail Barcode](https://postalref.com/products/intelligent-mail-barcode.md)
- [Intelligent Mail container barcode](https://postalref.com/products/intelligent-mail-container-barcode.md)
- [Intelligent Mail tray barcode](https://postalref.com/?q=Intelligent%20Mail%20tray%20barcode)
- [Intelligent Mail Tray Label](https://postalref.com/products/intelligent-mail-tray-label.md)
- [Postal Alphanumeric Encoding Technique](https://postalref.com/guides/intelligent-mail.md#other-barcodes)
- [Postal Intelligent Mail barcode](https://postalref.com/guides/intelligent-mail.md#other-barcodes)
- [Postal Numeric Encoding Technique](https://postalref.com/guides/intelligent-mail.md#other-barcodes)
- [Redirection Intelligent Mail barcode](https://postalref.com/guides/intelligent-mail.md#other-barcodes)
- [Routing Code](https://postalref.com/guides/intelligent-mail.md#imb)
- [Serial Number](https://postalref.com/guides/intelligent-mail.md#imb)
- [Service Type Identifiers](https://postalref.com/products/stids.md)
- [static IMb](https://postalref.com/guides/intelligent-mail.md#imb)
- [unique IMb](https://postalref.com/guides/intelligent-mail.md#imb)

### Documents (2)

- [Intelligent Mail Barcode 4-State Specification](https://postalref.com/guides/intelligent-mail.md#encoding)
- [Service Type IDentifier (STID) Table](https://postalref.com/guides/intelligent-mail.md#imb)

### Terms (10)

- [Constant fields](https://postalref.com/products/intelligent-mail-tray-label.md#terms)
- [dots per inch](https://postalref.com/products/intelligent-mail-tray-label.md#terms)
- [Intelligent Mail](https://postalref.com/products/intelligent-mail-barcode.md#terms)
- [Quiet Zone](https://postalref.com/guides/intelligent-mail.md#print-quality)
- [Reflectance Maximum](https://postalref.com/guides/intelligent-mail.md#print-quality)
- [Reflectance Minimum](https://postalref.com/guides/intelligent-mail.md#print-quality)
- [serialization strategy](https://postalref.com/products/intelligent-mail-tray-label.md#terms)
- [Symbol Contrast](https://postalref.com/guides/intelligent-mail.md#print-quality)
- [Variable fields](https://postalref.com/products/intelligent-mail-tray-label.md#terms)
- [X-dimension](https://postalref.com/guides/intelligent-mail.md#print-quality)

## Sources

[^1]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=6), page 1: “The IMb is a height-modulated barcode that encodes up to 31 digits of mailpiece data into 65 vertical bars using a 4-state symbology. … Mailers primarily apply the IMb. … However, due to the multiple benefits achieved by combining tracking and routing information into a single barcode, the Postal Service has now defined formats of the IMb intended for production and utilization solely by the Postal Service. … consists of four types of bars (the four states) … This document provides the specifications for generating and printing the Intelligent Mail® barcode (IMb) used in the U.S. Postal Service (USPS) mailstream.”

[^2]: [Steps to Create the Intelligent Mail® Barcode](https://postalpro.usps.com/mnt/glusterfs/2017-08/219_USPSIMB-Getting-Started_0.pdf#page=1), PDF page 1: “The Intelligent Mail barcode consists of a 20-digit Tracking Code (Barcode Identifier, Service Type Identifier, Mailer Identifier, and Serial Number) and a Routing Code (ZIP Code™) field of up to 11 digits. … A Mailer Identifier (Mailer ID or MID) is required for the IMb. … New Mailer IDs are assigned through centralized USPS processes, generally the Business Customer Gateway.”

[^3]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=111), page 107: “A label format for trays, tubs, and sacks that include a unique 24-digit Intelligent Mail tray barcode and human-readable routing information. … A 24-digit barcode that is used on the Intelligent Mail tray labels. … The IMtb uses the ISS Code 128 symbology. … The barcode identifies the destination ZIP Code, the contents of the tray, processing information, the mailer, and the unique serial number for the tray.”

[^4]: [Intelligent Mail Container Barcode Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2025-10/Barcode%20Tech%20Specifications_0.pdf#page=4), page 1: “The IMcb must consist of a 21-character data string encoded as either a linear, one-dimensional GS1-128 or a two-dimensional GS1 DataMatrix barcode. … The IMcb is used on mailer-generated pallet labels or placards to uniquely identify pallets and similar containers (i.e., All-Purpose Containers, hampers, pallet boxes, etc.) in addition to identifying the mail owner.”

[^5]: [Quick Step Guide to Mailer Identifier (MID) and/or CRID Acquisition](https://postalpro.usps.com/mnt/glusterfs/2018-03/QuickStepGuidetoMailerIdentifier(MID)CRIDAcquisition.pdf#page=1), page 1: “A Mailer ID (MID) is required when constructing all IMbs, including IMbs for mailpieces, handling units, and containers.”

[^6]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=110), page 106: “These 65 bars encode a string of 31 digits, divided into two parts: a 20-digit tracking code and an 11-digit routing code (when required). … The barcode encodes tracking information that identifies the mailer, type of service, and serial number and the routing code and routing information that contains the delivery point ZIP Code. … The IMb can combine into a single barcode the data of the POSTNET and PLANET Code barcodes, as well as other data. … A parcel barcode that is similar in purpose to the Intelligent Mail barcode for letters and flats.”

[^7]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=21), page 16: “Depending on the Service Type Identifier specified by the IMb, the human-readable representation of the barcode may need to be printed.”

[^8]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=22), page 17: “The fields of the tracking code, as defined in 2.1.3, shall be separated with a space added between data fields. … Using the 4th example in Table 5 in 2.2.1.3, the human-readable information will appear as follows: 01 234 567094 987654321 01234 5678 91. … The human-readable information, when required, shall be printed using a sans serif font and a minimum of 10- to 12-point size type. … Mailers as well as the Postal Service shall perform routine physical inspection and testing of Intelligent Mail barcodes to ensure the quality of labels produced.”

[^9]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=49), page 49: “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.”

[^10]: [Intelligent Mail® Barcode Technical Resource Guide](https://postalpro.usps.com/mnt/glusterfs/2017-08/221_USPSIMB-Tech-Resource-Guide.pdf#page=10), page 10: “To facilitate the adoption of the Intelligent Mail barcode, the Postal Service has developed, and is making available at no charge, a web-based, interactive encoder-decoder tool, and an extensive library of encoding software and fonts suitable for encoding and printing the Intelligent Mail barcode in mail production environments using selected operating systems and printing architectures. … The encoder will return the status of the encoding function along with a 65-character string of the letters F, A, D, or T, representing a full bar, ascender, descender, or tracker, respectively. … For example, a tracking code of 00040123456200800001 and a routing code of 987654321 will be encoded into the following 65-character string: … ADTTTATTTFTDFADTDTFTAATATADDDDFTTDTDFFDFTTATAFFDDADDTFFADFDFTTTAD … These resources are available from the same PostalPro web site. … Encoding data into a POSTNET or PLANET Code is very straightforward: each digit in the payload is represented by a predefined pattern of 5 bars. … The encoding algorithm that translates the 31 digits in the payload into 65 bars is defined in the USPS publication, Specification USPS-B-3200, which is available for download from PostalPro. … Each call to the encoder requires two arguments: a 20-digit tracking code, and none, 5, 9, or 11-digit routing code. … For each operating system, the encoding software package is distributed as a standard ZIP file. … A user guide is included in each package to provide detailed operating system and language-specific instructions on how to install and use the files in the package.”

[^11]: [Intelligent Mail® Barcode FAQ](https://postalpro.usps.com/mnt/glusterfs/2022-05/IMb_FAQ_5222v4.pdf#page=2), PDF page 2: “The 31-digit Intelligent Mail barcode contains 65 bars. … Vertical dimensions shall be based on the centerline of the barcode, forming an overall barcode height of 0.125 inch to 0.165 inch. … Horizontal dimensions shall be based on the centerline of the individual bars, forming an overall barcode pitch of 22 ±2 bars per inch. … Length - The distance from the lead (left) edge of the 1st (left most) bar to the lead (left) edge of the 65th (right most) bar shall never be less than 2.667 inches. … The distance from the lead (left) edge of the 1st bar (left most) to the trail (right) edge of the 65th (right most) bar shall never be greater than 3.225 inches. … On letters, it can be placed either in the address block or in the barcode clear zone found on the lower right corner of the envelope. … On flats, the Intelligent Mail barcode can be placed anywhere on the address side as long as it is at least 1/8th inch from any edge of the piece. … A minimum clear zone shall be 0.028 inch above and below the barcode and 0.125 inch on each end of the barcode.”

[^12]: [PostalPro: Intelligent Mail® Barcode](https://postalpro.usps.com/mailing/intelligent-mail-barcode): “The Intelligent Mail barcode is a 65-bar Postal Service™ barcode used to sort and track letters and flats. … The IMb is required for use on letters and flats prepared for automation prices.”

[^13]: [Federal Register: POSTNET Barcode Discontinuation (77 FR 26185, May 3, 2012)](https://www.govinfo.gov/content/pkg/FR-2012-05-03/html/2012-10505.htm): “DATES: Effective date: January 28, 2013. … The Postal Service will revise the Mailing Standards of the United States Postal Service, Domestic Mail Manual (DMM[supreg]) throughout various sections to discontinue price eligibility based on the use of POSTNETTM barcodes on all types of mail. … For automation letters and flats and for Qualified Business Reply Mail (QBRM), an Intelligent Mail barcode (IMbTM) will be required.”

[^14]: [PostalPro: Intelligent Mail Barcode (IMb) Encoder Software and Fonts](https://postalpro.usps.com/mailing/encoder-software-and-fonts): “The Postal Service provides Intelligent Mail® barcode files, fonts and encoders, available for download. … For printing Intelligent Mail® barcodes in a production environment, a variety of Intelligent Mail barcode fonts are available for 5 major production printing environments: AFP (MVS, AS/400, VM, VSE), HP PCL, PostScript, Xerox Metacode, and TrueType. … a world-wide, revocable, license to use them in the mailing industry without paying the Postal Service a royalty or other fee … The Postal Service provides software support for 24 combinations of language environments (C, Java 2, COBOL, and PL/1) on 9 unique platforms (z/OS, VSE/ESA, OS/400, AIX, Linux, Solaris, HP/UX, Mac, and Windows).”

[^15]: [Steps to Create the Intelligent Mail® Barcode](https://postalpro.usps.com/mnt/glusterfs/2017-08/219_USPSIMB-Getting-Started_0.pdf#page=2), PDF page 2: “Once mailers have selected service(s), received their MID, and devised a unique serial number strategy, they are ready to put the five fields together to form the 20- to 31-digit string, encode it to 65 characters, and convert the 65-character string using the IMb font to form the 65-bar Intelligent Mail barcode as in the example below. … Depending on the length of the MID, the Serial Number is either a nine- or six-digit number.”

[^16]: [Intelligent Mail® Barcode FAQ](https://postalpro.usps.com/mnt/glusterfs/2022-05/IMb_FAQ_5222v4.pdf#page=3), PDF page 3: “A USPS-assigned 6 or 9-digit (depending on mail volume) field used to identify the mail owner or mail preparer. … A 2-digit field reserved to encode the presort identification printed in human-readable form on the Optional Endorsement Line (OEL). … A 3-digit field used to identify the class of mail and any additional or special services requested for the piece. … A 6 or 9-digit field (depending on MID) defined by the mailer.”

[^17]: [PostalPro: Intelligent Mail® for Small Business Mailers (IMsb)](https://postalpro.usps.com/mailing/imsb): “Intelligent Mail® for Small Business Mailers (IMsb) is a free online tool which will allow you to produce the presorted Intelligent Mail barcodes (IMb) for your mail pieces, tray labels and submit an electronic postage statement to the acceptance units. … To use the IMsb, no special software or installation is required. Users simply access the application via a web browser.”

[^18]: [Intelligent Mail® Barcode Technical Resource Guide](https://postalpro.usps.com/mnt/glusterfs/2017-08/221_USPSIMB-Tech-Resource-Guide.pdf#page=11), page 11: “To avoid ambiguity, only one Intelligent Mail barcode can be placed in the same area.”

[^19]: [Intelligent Mail® Barcode Technical Resource Guide](https://postalpro.usps.com/mnt/glusterfs/2017-08/221_USPSIMB-Tech-Resource-Guide.pdf#page=9), page 9: “Also, unlike POSTNET barcode, the Intelligent Mail barcode is always 65 bars regardless of ZIP Code length. … The Routing Code, if populated, must never be padded with zeros, spaces or nulls that are not part of the valid ZIP Code.”

[^20]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=8), page 3: “Total Barcode String Length: the overall length of the barcode string supplied to the encoder routine can be one of four values depending on the amount of Routing Code information provided. … The Routing Code length varies depending on the amount of routing information available and may be 0, 5, 9, or 11 digits. … 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. … NOTE: No error detection and correction, such as a checksum, shall be included as part of the data fields; error detection and correction shall be added as part of the encoding process.”

[^21]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=174), page 170: “A POSTNET barcode can represent a 5-digit ZIP Code (32 bars), a 9-digit ZIP+4 code (52 bars), or an 11-digit delivery point code (62 bars). … When separated into groups of five, these bars sequentially represent each of the digits of the ZIP Code (or ZIP+4 code or delivery point code) for the delivery address, plus an additional digit designated as the correction digit.”

[^22]: [Appendix B: ACS™ Frequently Asked Questions](https://postalpro.usps.com/mnt/glusterfs/2026-04/AppendixB_ACSFAQ.pdf#page=7), page 7: “Obtain a hand held scanner or contact your local USPS Mailpiece Design Analyst.”

[^23]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=27), page 23: “Barcodes are used on individual mailpieces as well as labels on larger units such as trays, sacks, and pallets containing mailpieces or containers containing larger units such as sacks or trays on pallets. … A label on a tray, sack, pallet, and other types of containers that bears a barcode that includes information about the mail inside the container and the origin and destination of the mail. … A rectangular area in the lower right part of a letter-size mailpiece that must be kept free of printing and symbols, except for the barcode itself.”

[^24]: [PostalPro: Service Type Identifiers (STIDs)](https://postalpro.usps.com/mailing/service-type-identifiers): “The STID defines the mailpiece as full-service or basic (non-automation) and is also used to determine the disposition of undeliverable-as-addressed (UAA) mail and the form of address correction that a mailer desires if any.”

[^25]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=96), PDF page 96: “The Full-Service Intelligent Mail option requires unique mailpiece barcodes, the use of Intelligent Mail barcodes on tray labels or container placards, electronic documentation, and the use of Facility Access and Shipment Tracking to schedule appointments for the entry of mailings. … (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.”

[^26]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=25), page 20: “The BCG gives you a single entry point for Postal Service online business services”

[^27]: [A Guide to Full Service](https://postalpro.usps.com/mnt/glusterfs/2018-03/AGuidetoFullService.pdf#page=8), page 2: “Ensure all containers, trays, and pieces have an Intelligent Mail Barcode that is unique for 45 days from the postage statement mailing date.”

[^28]: [Informed Visibility® Mail Tracking & Reporting (IV®-MTR) Mail.XML Guide](https://postalpro.usps.com/mnt/glusterfs/2026-09/MTR_MailXMLGuide_v3.1.pdf#page=7), page 7: “IMb Tracing ® (formerly CONFIRM®) was the source for automated piece and bundle tracking data, while PostalOne!® was the source for container and handling unit tracking data. … Mail tracking functionality for containers, handling units, bundles, and pieces is consolidated into IV-MTR, which is the new and comprehensive mail data repository for the Postal Service™. … The application provides near real-time tracking information for all letters, flats, and mail aggregates, which includes containers, handling units, and bundles.”

[^29]: [Informed Visibility® Mail Tracking & Reporting (IV®-MTR) User Guide](https://postalpro.usps.com/mnt/glusterfs/2026-09/IV_MTR_UserGuide_v2.19.9.pdf#page=31), page 19: “The legacy PKG file format allows you to receive files in the format used by the retired IMb Tracing system.”

[^30]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=23), page 18: “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. … The PLANET Code is a legacy 12-digit (long and short bars) barcode used to track mail electronically. … The IMb has replaced the use of the POSTNET barcode. … The IMb has replaced the use of the PLANET Code.”

[^31]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=85), page 81: “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. … It is printed to the left of the indicia, along the top edge of a letter or card and is used to identify Business Reply Mail, automation-compatible courtesy reply envelopes, metered reply mail, InformationBased Indicia or PC Postage mail, and other designated types of mail. … Different combinations of bars represent different types of mail.”

[^32]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=17), page 12: “A clear zone shall be placed around the barcode to ensure that readers can locate and read the barcode.”

[^33]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=7), page 2: “The Tracking Code component shall be made up of 20-digits that that will be used for identification and tracking purposes.”

[^34]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=10), page 5: “The Routing Code shall contain the Delivery Point ZIP Code™ for routing the mailpiece to its final delivery point. … An encoder is required to convert the digits into a 65-character string representing the bars of the IMb, and a special font is required to convert the 65-character string into the IMb itself.”

[^35]: [Barcode Identifier](https://postalpro.usps.com/mnt/glusterfs/2017-01/BarcodeIdentifier.pdf#page=1), PDF page 1: “Generally, this field should be left as “00” (zero-zero) if an OEL is not printed on the mailpiece. … The exception is for automation-rate eligible flat mail with an optional endorsement line, where the Intelligent Mail barcode must contain OEL coding corresponding to the correct sortation level of each piece.”

[^36]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=44), page 44: “A series of specific printed characters on the top line of the address block that identifies the sortation level of a bundle and may contain an ACS participant code.”

[^37]: [A Guide to Full Service](https://postalpro.usps.com/mnt/glusterfs/2018-03/AGuidetoFullService.pdf#page=17), page 11: “The 15-digit MID/serial number combination can’t be repeated in FullService mailings of the same class within 45 calendar days of the mailing date. … Full-service mailpieces are required to have a unique IMb; basic automation option mailpieces are not. … The uniqueness of a mailpiece IMb is determined by the six or nine-digit MID, the six or nine-digit serial number, and the piece’s class, indicated by the STID. … Full-Service uniqueness for these labels is based on the entire 24-digit (trays/sacks) or 21-digit (container) barcode. … 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.”

[^38]: [Publication 600: Share Mail](https://about.usps.com/publications/pub600.pdf#page=7), PDF page 7: “The ability to print on each mailpiece either a static IMb (a barcode that does not vary by mailpiece) or a unique IMb (a barcode that does vary by mailpiece). … a barcode that does vary by mailpiece … a barcode that does not vary by mailpiece”

[^39]: [Service Type Identifier (STID) Quick Service Guide](https://postalpro.usps.com/mnt/glusterfs/2021-05/STIDQuickServiceGuide.pdf#page=1), PDF page 1: “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.”

[^40]: [Mailer's Technical Advisory Committee - Best Practices for ACS™](https://postalpro.usps.com/mnt/glusterfs/2022-05/ACS_BestPractices.pdf#page=45), page 45: “The portion of the Intelligent Mail barcode that identifies a single piece of mail. … The portion of the Intelligent Mail barcode that contains the ZIP Code for the address on the mail piece.”

[^41]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=228), PDF page 228: “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. … 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.”

[^42]: [Ballot Mail & Political Mail STIDs Fact Sheet](https://postalpro.usps.com/mnt/glusterfs/2025-10/23108_BALLOT%20MAIL%20AND%20POLITICAL%20MAIL_STID%20Tables%20Fact%20Sheet_Jan%202024%20Final(508-Compliant).pdf#page=1), PDF page 1: “A unique three-digit code embedded in the Intelligent Mail® barcode (IMb®) that indicates the service type for an individual mailpiece.”

[^43]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=22), PDF page 22: “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.”

[^44]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=65), page 61: “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.”

[^45]: [PostalPro: Intelligent Mail® Tray Label](https://postalpro.usps.com/mailing/intelligent-mail-tray-label): “Each 24-digit label uniquely identifies each tray, tub, and sack as well as the originator of each handling unit as it makes its way throughout the Postal Service's mail processing and transportation networks.”

[^46]: [PostalPro: Intelligent Mail® Container Barcode (IMcb)](https://postalpro.usps.com/mailing/intelligent-mail-container-barcode): “It is used on mailer-generated pallet labels to uniquely identify pallets and similar containers (i.e. All Purpose Containers, hampers, pallet boxes, etc.) in addition to identifying the mail owner and, it provides a link between the electronic mailing record and the physical mail aggregate. … 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.)”

[^47]: [Intelligent Mail Tray Label Technical Fact Sheet](https://postalpro.usps.com/mnt/glusterfs/2025-07/Intelligent%20Mail%20Tray%20Label%20Technical%20Fact%20Sheet%20IMbg%20July%202025.pdf#page=2), PDF page 2: “For 5-digit trays in accordance with the DMM®, the destination ZIP Code is the 5-digit ZIP Code. … For 3-digit trays in accordance with the DMM, the destination ZIP Code is the 3-digit ZIP Code followed by two zeros. … Describes the contents of the tray or sack based on the 3-digit content identifier numbers (CIN) listed in the DMM.”

[^48]: [DMM 204: Barcode Standards](https://pe.usps.com/text/dmm300/204.htm): “Intelligent Mail tray labels are designed for optimum use with Intelligent Mail barcoded mail and have the capacity to provide unique identification throughout postal processing, but are required for use on all trays and sacks in presorted mailings.”

[^49]: [DMM 203: Basic Postage Statement, Documentation, and Preparation Standards](https://pe.usps.com/text/dmm300/203.htm): “Barcoded tray labels must be used for automation-price letter-size mailings, automation-price flat-size mailings, and flat-sized mailings cobundled and cotrayed under”

[^50]: [Intelligent Mail Tray Label Technical Fact Sheet](https://postalpro.usps.com/mnt/glusterfs/2025-07/Intelligent%20Mail%20Tray%20Label%20Technical%20Fact%20Sheet%20IMbg%20July%202025.pdf#page=1), PDF page 1: “The use of the IM tray label does not require the mailer to satisfy Full-Service requirements and is not an indicator that the mailer qualifies for the Full-Service option.”

[^51]: [Guide to eInduction](https://postalpro.usps.com/mnt/glusterfs/2026-08/375_Guide-to-eInduction_1.pdf#page=15), page 14: “Must begin with 99M … Must be twenty-one characters long”

[^52]: [Intelligent Mail Tray Label 10-Digit and 10/24-Digit Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2020-02/IMTL_10_1024_SPECIFICATIONS_FOR_MAILERS_SPUSPS-L-3191.pdf#page=47), page 47: “The applicable 3-Digit CIN that correctly describes the contents of the tray or sack based on the Mailer CIN List in the DMM.”

[^53]: [Intelligent Mail Tray Label 10-Digit and 10/24-Digit Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2020-02/IMTL_10_1024_SPECIFICATIONS_FOR_MAILERS_SPUSPS-L-3191.pdf#page=12), page 12: “the 3 or 5-digit ZIP Code for the tray or sack’s destination, or the ZIP Code of the mail within the container”

[^54]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=63), page 59: “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.). … The DP is encoded within the POSTNET or Intelligent Mail barcode.”

[^55]: [Mail.xml Technical Specifications R65.0.0.0 ](https://postalpro.usps.com/mnt/glusterfs/2026-10/eDoc-XML-Tech_Spec.pdf#page=320), page 320: “POSTNET barcode is not eligible for Automation pricing.”

[^56]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=59), page 54: “A USPSapplied IMb is identified by the use of specific Postal Use Only Barcode ID values that indicate that a specific IMb is constructed differently from the mailer IMb. … Setting aside the Routing Code field, this allows 18 digits (STID, MID, and serial number fields) to be used in lieu of the ID Tag information contained in the USPS letter mail ID Tag. … 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.”

[^57]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=61), page 56: “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. … A mailpiece that has no mailer-applied IMb may still be redirected but will have a pIMb applied by the USPS MPE and not an rIMb.”

[^58]: [Intelligent Mail® Barcode FAQ](https://postalpro.usps.com/mnt/glusterfs/2022-05/IMb_FAQ_5222v4.pdf#page=1), PDF page 1: “The Postal Service Flat Mail Identification Code Sort (FICS) program uses another type of 4-state barcode that looks similar to the Intelligent Mail barcode, but it is applied as an ID tag on non-barcoded flat mail pieces only.”

[^59]: [Full-Service Certification Standards](https://postalpro.usps.com/mnt/glusterfs/2024-05/FS%20Certification%20Standards%20and%20Application%20Form%20May%202024_0.pdf#page=63), page 63: “FIM E is used for postcard-size and letter-size First-Class Mail with Share Mail.”

[^60]: [Intelligent Mail® Barcode (IMb) 4-State Specification](https://postalpro.usps.com/mnt/glusterfs/2017-08/2190_USPSB3200IntelligentMailBarcode4State_0.pdf#page=19), page 14: “When measured with a Postal Service envelope reflectance meter or equivalent, the minimum reflectance from the background area shall be 50 percent in the red portions and 45 percent in the green portions of the optical spectrum. … 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. … The minimum PRD shall be at least 30 percent in the red and green portions of the optical spectrum. … Within the clear areas around the barcode, background patterns, envelope insert “show through,” and all other printing shall be limited to a maximum print contrast ratio (PCR) of 15 percent when measured in the red and green portions of the optical spectrum using a Postal Service envelope reflectance meter or equivalent.”

[^61]: [Intelligent Mail Tray Label 10-Digit and 10/24-Digit Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2020-02/IMTL_10_1024_SPECIFICATIONS_FOR_MAILERS_SPUSPS-L-3191.pdf#page=31), page 31: “All barcodes in each mailing shall measure American National Standards Institute (ANSI) grade A, B, or C. … At least 70 percent of the barcodes shall measure American National Standards Institute (ANSI) grade A or B and none of the remaining portion shall measure lower than ANSI grade C when measured with a 10 mils aperture (0.250 mm) in light in the red spectral range between 630 nanometers (nm) and 675 nm.”

[^62]: [Intelligent Mail Container Barcode Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2025-10/Barcode%20Tech%20Specifications_0.pdf#page=7), page 4: “The reflectance value of the darkest bar within the bar code symbol (R min) must be equal to or less than half the reflectance value of the lightest space (Rmax), when measured in the red spectral range between 630 nanometers (nm) and 675 nm. … The symbol contrast must be greater than 40 percent. … Encoding the IMcb Using the GS1-128 Format … The width of the narrowest bar or space element within the barcode symbol is defined as the X-dimension. … The barcode must be printed with an X-dimension that must measure between 0.0225-inch (22.5-mils) and 0.0275-inch (27.5-mils). … A printer with a minimum dots per inch (DPI) of 203 is required for printing the IMcb; however, a printer of 300 DPI or greater is recommended.”

[^63]: [Intelligent Mail Container Barcode Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2025-10/Barcode%20Tech%20Specifications_0.pdf#page=9), page 6: “Encoding the IMcb Using the GS1 DataMatrix Format … The barcode must be printed with an X-dimension of 0.075 inch (75 mils) ± 0.002 inch (2 mils).”

[^64]: [Intelligent Mail Tray Label 10-Digit and 10/24-Digit Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2020-02/IMTL_10_1024_SPECIFICATIONS_FOR_MAILERS_SPUSPS-L-3191.pdf#page=6), page 6: “A printer with a minimum dpi of 203 is required for printing the IM tray labels.”

[^65]: [Publication 199: Intelligent Mail Package Barcode (IMpb) Implementation Guide for Confirmation Services and Electronic Payment Systems](https://postalpro.usps.com/mnt/glusterfs/2026-07/Pub%20199_v35_07022026.pdf#page=474), page 475: “Highest reflectance value, normally the reflectance value of the lightest space within the barcode symbol, including the quiet zones. … Lowest reflectance value, normally the reflectance value of the darkest bar within the barcode symbol, including the quiet zones. … 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.””

[^66]: [Publication 199: Intelligent Mail Package Barcode (IMpb) Implementation Guide for Confirmation Services and Electronic Payment Systems](https://postalpro.usps.com/mnt/glusterfs/2026-07/Pub%20199_v35_07022026.pdf#page=475), page 476: “Difference between the highest reflectance value and the lowest reflectance value anywhere in the scan reflectance profile, including the quiet zones. … The nominal width of the narrowest bar or space element within the barcode symbol is defined as the X-dimension.”

[^67]: [A Guide to Full Service](https://postalpro.usps.com/mnt/glusterfs/2018-03/AGuidetoFullService.pdf#page=11), page 5: “Full-Service feedback will not be provided for a bundle, handling unit, or container that has a non-unique barcode or an invalid mail owner.”

[^68]: [A Guide to Full Service](https://postalpro.usps.com/mnt/glusterfs/2018-03/AGuidetoFullService.pdf#page=86), page 80: “If the same MID and Serial Number are used on two mailpieces with two different STIDs that indicate the same class of mail (for example First-Class STIDs 314 and 320), those pieces will be flagged as non-unique.”

[^69]: [Guide to eInduction](https://postalpro.usps.com/mnt/glusterfs/2026-08/375_Guide-to-eInduction_1.pdf#page=24), page 23: “A Duplicate error is logged when the same IMcb is used on two or more containers within 45 days of the eDoc Postage Statement Mailing Date.”

[^70]: [SingleSource ACS™ Technical Guide ](https://postalpro.usps.com/mnt/glusterfs/2019-10/SingleSourceACSTechGuide.pdf#page=19), page 19: “The following are the most common issues that can interfere with the creation, fulfillment, and use of ACS: … The Mailer ID embedded in the barcode (or Participant ID) is either not present or incorrect. … STID used in the IMb is either not present or does not request ACS. … The serial number is all zeroes or not unique for each mailpiece. … IM barcodes located in the lower right corner of a letter will generally take precedence over an IM barcode in the address block.”

[^71]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=41), page 37: “An Ancillary Service endorsement printed on mail by the sender that directs USPS to handle undeliverable-as-addressed mail according to the option selected by the sender: (a) Option 1, the mail is disposed of; (b) Option 2, the mail is forwarded if a change-of-address order is on file and a notice of the new address is provided to the sender or the mail is disposed of if it cannot be forwarded.”

[^72]: [Publication 32: Glossary of Postal Terms](https://postalpro.usps.com/mnt/glusterfs/2016-04/pub32_glossary.pdf#page=197), page 193: “An Ancillary Service endorsement printed on mail by the sender that directs USPS to return undeliverable-as-addressed mail with the new address or the reason for nondelivery attached.”

[^73]: [Appendix A: Ancillary Service Type Identifier (STID) Details](https://postalpro.usps.com/mnt/glusterfs/2024-02/Appendix%20A.pdf#page=28), page 26: “First-Class Mail can be discarded only if ACS can be generated, therefore if the IMb cannot be read, and the allowable printed endorsement "Change Service Requested" is used, the mail may be treated as if endorsed "Return Service Requested" and will be returned to the sender if UAA.”

[^74]: [Intelligent Mail Tray Label 10-Digit and 10/24-Digit Technical Specifications](https://postalpro.usps.com/mnt/glusterfs/2020-02/IMTL_10_1024_SPECIFICATIONS_FOR_MAILERS_SPUSPS-L-3191.pdf#page=16), page 16: “Perforations are not permitted through the barcode and barcode clear zones on the labels.”

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