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Intelligent Mail Matrix Barcode

The Intelligent Mail Matrix Barcode, IMmb for short, is a two-dimensional GS1 DataMatrix barcode that USPS uses to route and track packages. It holds the same data as the package's Intelligent Mail Package Barcode, the linear IMpb. The IMmb lets USPS still read a package when its IMpb becomes unreadable.

Updated October 28, 202615 sources

What it is

The IMmb is a supplemental barcode that USPS adds to its standard shipping label layouts. It works together with the IMpb to make processing more efficient.

Curves, fold-overs and creases on soft packs and irregular parcels can distort the IMpb until it can't be read. An unreadable IMpb lowers the package's visibility to the customer and can mean a re-run or a manual sort. USPS put the IMmb into use in 2023.

The two barcodes differ in how they draw the same data. The IMmb is a two-dimensional GS1 DataMatrix, and the IMpb is a linear GS1-128 barcode. GS1 DataMatrix takes less space, and its Reed-Solomon error correction can let a damaged barcode still be read. The smaller symbol lets two IMmbs fit in unused areas of a standard shipping label.

Every USPS platform prints the IMmb, Click-N-Ship among them. Mail service providers, shipping solution vendors and PC Postage companies can print it too.

How it works

A label carries the IMpb and one or two IMmbs, all holding the same data. With two IMmbs, a package has three chances to be scanned and tracked. The repeated data raises the volume and quality of scans that processing equipment collects.

An IMmb holds its label's IMpb data, such as this example tracking number from the check-digit procedure.

9212391234567812345670

The Mailer ID and serial number are examples.

    The payload keeps the IMpb's GS1 application identifiers and both of its Function 1 characters. An IMmb needs no banner, human-readable text or identification bars.

    Where it goes on the label

    The IMmb belongs in two segments of the label: Address and Delivery Information, and Additional Information and User. The IMmb in the Address and Delivery Information segment is required. The one in the Additional Information and User segment is optional but recommended.

    In the Address and Delivery Information segment, the IMmb sits directly to the left of the delivery address. The delivery address may need more indentation to leave room for the IMmb's quiet zone and margins. On a smaller label, such as the 6x3 label, this IMmb may move to the left of the return address.

    In the Additional Information and User segment, the IMmb is right justified, again leaving room for its quiet zone and margins. USPS recommends this second IMmb in the lower right corner of the label.

    The symbol

    The IMmb uses the square form of GS1 DataMatrix. It is 20x20 modules, with a data region of 18x18 modules. Its printed size follows from the modules and the X-dimension.

    The X-dimension is between 0.019 inch and 0.022 inch. An X-dimension of 0.02 inch is recommended. It stays the same throughout the symbol.

    Print quality is graded under ISO/IEC 15415. The darkest bar's reflectance is at most half the lightest space's, measured in red light between 630 nm and 675 nm. Symbol contrast must be greater than 40 percent.

    Rules

    At least one IMmb, located in the Delivery Address section of the Address and Delivery Information segment is required on all USPS parcel shipping labels.

    Every USPS parcel shipping label must carry at least one IMmb, beside the delivery address. The requirement takes effect January 19, 2025.

    Takes effect January 19, 2025

    The data payload of the IMmb shall match the traditional, GS1-128 Intelligent Mail Package Barcode (IMpb).

    The IMmb must carry exactly the data in the IMpb on the same label.

    All classes of parcel mail (with the exception of BPM NonPresorted) are required to apply IMpb & IMmb barcodes as defined in DMM 204.2.1.1.

    Every class of parcel mail must carry both an IMpb and an IMmb. Bound Printed Matter NonPresorted is the one exception.

    An IMmb is optional but recommended in the Additional Information and User segment.

    Mailers should add a second IMmb in the Additional Information and User segment, though it is optional.

    The IMmb must be oriented such that the “L” finder pattern is located in the lower, left-hand corner of the barcode when the label is viewed in a standard upright, portrait mode position.

    The L-shaped finder pattern must sit in the lower left corner when the label is upright.

    A clear zone equal to five times (5X) the X-dimension, but no less than 0.1 inches, must be maintained around all four sides of the IMmb.

    A quiet zone must surround all four sides of the IMmb. It must be at least five times the X-dimension, and never less than 0.1 inch.

    At least 70 percent of the barcodes in each mailing shall have an overall symbol grade of “B” or better when measured with the appropriate aperture size in the red spectral range between 630 nanometers (nm) and 675 nm.

    At least 70 percent of the IMmbs in a mailing must grade B or better. The rest must grade no lower than C.

    What goes wrong

    USPS is updating its systems to detect a missing IMmb on every shipping label. Package Quality Noncompliance assessments for a missing or mismatched IMmb began January 19, 2025 for hazardous materials packages. They began April 1, 2025 for all other packages.

    Mailers pay the Package Quality Noncompliance fee when noncompliant pieces exceed the threshold for barcode, manifest or address quality. The fee is $0.25 a piece. Paying it doesn't exempt a mailer from the barcode requirements.

    A mailing presented without the required IMpb, IMmb and electronic file may be rejected, or its parcels intercepted. USPS intercepts such parcels to protect the mail and cut revenue lost to fraudulent packages.

    Terms

    Intelligent Mail Package BarcodeIMpb
    An IMpb is the USPS-developed barcode that can be read by automated parcel-processing equipment and scanning devices and consists of a data string that generally follows the GS1-128 specification.
    GS1 DataMatrix
    A special type of DataMatrix barcode conforming to a structure defined byGS1.
    GS1-128 Barcode SymbologyGS1-128
    A subset of the more general Code 128 that is utilized exclusively for GS1 System data structures.
    GS1 Application IdentifierAI, Application Identifier
    GS1 Application Identifiers are a specific set of defined identifiers used to connect physical and logical things to information or business messages related to them. This field of two or more characters at the beginning of an Element String uniquely defines format and meaning of the string.
    Function 1 characterFNC1, Function 1
    A symbology character used in some GS1 data carriers for specific purposes.
    X-dimension
    The nominal width of the narrowest bar or space element within the barcode symbol is defined as the X-dimension.
    Quiet Zoneclear 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.”
    Symbol ContrastSC
    Difference between the highest reflectance value and the lowest reflectance value anywhere in the scan reflectance profile, including the quiet zones.
    Bound Printed MatterBPM, BP
    Bound Printed Matter is typically catalogs, directories, books, and other printed material that weigh up to 15 pounds and meet specific eligibility standards

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    Technical Specifications

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