USPS Definitions and Descriptions

AADC (automated area distribution center)

An area distribution center (ADC) that uses multiline optical character readers (MLOCRs), barcode sorters (BCSs), and other equipment designed for processing automation-compatible mail. Also see ADC.

ACS (Address Change Service)

An automated process that provides change-of-address information to mailers who maintain computerized mailing lists. The information is captured in the Computerized Forwarding System (CFS) units and sent to mailers on electronic media to eliminate manual processing of change information. The cost is less than manual notices.

ADC (area distribution center)

A mail processing facility that receives and distributes mail destined for specific ZIP Code areas under the Managed Mail Program (MMP). An ADC is one of the points within the national MMP distribution network.

AEC (Address Element Correction)

A process that revises incomplete or incorrect address files and then attaches ZIP+4 and carrier route codes. It involves computer matching of records that cannot be coded using CASS-certified software.

BC (barcode)

A series of vertical bars and half bars that represents the correct ZIP Code information for the delivery address on a mailpiece. The barcode facilitates automated processing by barcode reader equipment. Each numeric digit is represented by a combination of two full bars and three half bars. A complete barcode contains two full bars framing the code; the five, nine, or eleven digits containing ZIP Code information; and a final correction digit that allows the machine to check its reading of the number. See also DPBC and postnet.

BCR (barcode reader)

A component in certain mail processing equipment that reads and interprets the barcode previously applied to a mailpiece.

BCS (barcode sorter)

A computer-controlled, high-speed machine that sorts letters and cards by using a barcode reader (BCR) to interpret an imprinted barcode. The BCS consists of a mail feed and transport unit, stackers (bins), and associated electronic equipment.

BMC (bulk mail center)

A highly mechanized mail processing plant that distributes Standard Mail (A) and Periodicals in bulk form and Standard Mail (B) in piece and bulk form.

BMEU (business mail entry unit)

The area of a postal facility where mailers present bulk or presort mail and mail entered under permit imprint for acceptance. The BMEU includes dedicated platform space, office space, and a staging area on the workroom floor. (Also called platform acceptance unit; formerly called bulk mail acceptance unit.)

BRM (business reply mail)

A domestic service that allows pieces bearing a specific address or label format to be mailed back to the addressee without prepayment of postage by the sender. Postage and fees are collected when the mail is delivered to the addressee who originally distributed the BRM.


A group of packages secured together into a single piece or unit under the standards applicable to the rate claimed. See also package.

CASS (Coding Accuracy Support System)

A service offered to mailers, service bureaus, and software vendors that improves the accuracy of delivery point codes, ZIP+4 codes, 5-digit ZIP Codes, and carrier route information on mailpieces. CASS provides a common platform to measure the quality of address matching software and useful diagnostics to correct software problems.

CR (carrier route)

The addresses to which a carrier delivers mail. In common usage, carrier route includes city routes, rural routes, highway contract routes, post office box section, and general delivery units.

CRIS (Carrier Route Information System)

A listing of all delivery address range information in a standardized format. CRIS contains schemes for city, rural, and highway contract routes and post office box sections. This information is formatted by ZIP Code, street name, and street number range.

CRM (courtesy reply mail)

Preaddressed postcards or envelopes that a mailer provides to its customers both to expedite and to provide more accurate delivery of their responses. Unlike BRM, CRM requires no permit fee and involves no charges for returned pieces because the respondent pays the reply postage.

DBMC (destination bulk mail center) rate

A discount/rate available to some rate categories of Standard Mail that is properly prepared and entered by the mailer at the BMC or other designated postal facility that serves the delivery address on the mail.

DDU (destination delivery unit) rate

A discount/rate available to Periodicals and Standard Mail (A) that is properly prepared and entered by the mailer at the delivery unit that serves the delivery address on the mail.

DMM (Domestic Mail Manual)

The USPS manual that contains the basic standards governing U.S. domestic mail services, descriptions of the mail classes and special services and conditions governing their uses; and standards for rate eligibility and mail preparation. Domestic mail is classified by size, weight, content, service, and other factors.

DPBC (delivery point barcode)

A POSTNET barcode that consists of 62 bars with beginning and ending frame bars and 5 bars each for the nine digits of the ZIP+4 code, the last 2 digits of the primary street address number (or post office box, etc.), and a correction digit. The DPBC allows automated sortation of mail to the carrier level in walk sequence.

drop shipment

Typically the movement of a mailer's product on private (nonpostal) transportation from the point of production to a postal facility located closer to the destination of the product. Express Mail and Priority Mail drop shipment service can be used instead of a private carrier.

DSCF (destination sectional center facility) rate

A discount/rate available to Periodicals and Standard Mail (A) that is properly prepared and entered by the mailer at the sectional center facility (SCF) that serves the delivery address on the mail (for Standard Mail) or in its service area (for Periodicals).

DVP (delivery point validation)

Required by the USPS to help identify inaccurate, incomplete, or erroneous addresses and validate accurate delivery point address information contained in mailer address files

FCM (First-Class Mail)

A class of mail that includes all matter wholly or partly in writing or typewriting, all actual and personal correspondence, all bills and statements of account, and all matter sealed or otherwise closed against inspection. Any mailable matter may be sent as First Class Mail

FIM (facing identification mark)

A series of vertical bars used by automated postal equipment to identify, orient, and separate business and courtesy reply mail. FIMs are required in the upper right corner of business replay mail.

flts (flats)

A code used on mail container labels that identifies the contents as flat-size mail (mail that exceeds at least one of the dimensions for letter-size mail).

IMM (International Mail Manual)

The USPS manual that contains classification regulations and other requirements for mailing between the United States and other countries.,


Imprinted designation on mail that denotes postage payment (e.g., permit imprint).


Optional information printed at least two lines above the address or in the lower left corner of the envelope. Under some postage payment systems, the keyline is a required line that contains specific information about the mailpiece.

LACS (locate Address conversion system)

Is an automated method to update rural rout addresses which have undergone a 911 conversion to street style addresses (example: RR1 Box 37 to Morrison Ave)

LTRS (letters)

A code used on mail container labels that identifies the contents as letter-size mail (mail, including cards, that does not exceed any dimension for letter-size mail).

MACH (machinable)

A code used on mail container labels that identifies the contents as machinable parcels (mail that does not exceed any dimension for mail that can be processed on mechanized parcel sorting equipment).

mailing statement

See postage statement.

MASS (Multiline [OCR] Accuracy Support System)

A tool similar to Coding Accuracy Support System (CASS) that accesses and checks the address matching software used by customers' multiline optical character readers (OCRs).

MLOCR (multiline optical character reader)

An OCR that reads and interprets multiple lines of the delivery address on a mailpiece.

MXD (mixed)

A code used on mail container labels that identifies the contents as mixed mail for different destinations (such as for multiple ADCs).

NCOA (National Change of Address) System

An address correction service that the USPS provides to mailers through USPS licensees. The licensees match mailing lists submitted to them on tape or disk against change-of-address information for the entire country from all Computerized Forwarding System units. NCOA can correct an address before it is used on a piece of mail.

NMO (nonmachinable outside)

A parcel or mailpiece that, because of size, weight, or other characteristic, cannot be safely sorted by mechanized mail processing equipment and must be handled manually. The parcel is called an outside because it cannot be placed in a sack or other mailing container.

OCR (optical character reader)

An automated mail sorting machine that interprets the address information on a letter-size mailpiece and sprays the corresponding ZIP Code information on to the piece as a barcode. The OCT consists of a mail feed unit, transport unit, stacker modules, computer with a control system, video monitor, and printer.

OEL (optional endorsement line)

A series of specific printed characters on the top line of the address block that identifies the sortation level of a package or bundle. The OEL is used in place of a pressure-sensitive adhesive package label.


A package is a group of addressed pieces assembled and secured together to make up a basic unit of bulk mail for processing purposes. The term is not correctly applied when referring to unsecured groups of pieces placed in trays and identified by separator cards, although package labels and other package identification methods may be used for unsecured groups of pieces as permitted by standard.

PAVE (presort Accuracy Validation and Evaluation)

A voluntary program in which the USPS provides testing for certain categories of presort software and hardware products to determine their accuracy in sorting address information according to Domestic Mail Manual (DMM) standards and producing standardized supporting documentation.


A class of mail (formerly called second-class) consisting of magazines, newspapers, or other publications formed of printed sheets that are issued at least four times a year at regular specified intervals (frequency) from a "known office of publication." Periodicals usually must have a list of subscribers, and/or requesters, as appropriate.


An authorization, typically a mailing permit or an authorization mail to without postage affixed, using an indicia containing specific information.


An individually addressed mailpiece. This definition also applies when piece is used in eligibility standards. Quantities indicated for optional or required sortations always refer to pieces unless specifically excepted.

postage statement

Documentation provided by a mailer to the USPS that reports the volume of mail being presented and the postage payable or affixed, and certifies that the mail meets the applicable eligibility standards for the rate claimed.

POSTNET (Postal Numeric Encoding Technique)

The barcode system for encoding the delivery point information and ZIP+4 code information on letter-size and flat-size mailpieces. Also see DPBC.

PRC (Postal Rate Commission)

An independent federal agency, created by the Postal Reorganization Act, that makes recommendations concerning USPS requests for changes in postal rates and mail classifications. The five Commissioners are nominated by the President and approved by the Senate.


The process by which a mailer prepares mail so that it is sorted to at least the finest extent required by the standards for the rate claimed. Generally, presort is performed sequentially, from the lowest (finest) level to the highest level, to those destinations specified by standard and is completed at each level before the next level is prepared. Not all presort levels are applicable in all situations.

presort levels

Terms used for presort levels are defined as follows:

RCSC (rates and classification service center)

A field office of Business Mail Acceptance that provides guidance to field personnel and customers on mail classification, postage rates, mail preparation, and postage payment programs.

RR (rural route)

A delivery route served by a rural carrier.

SCF (sectional center facility)

A postal facility that serves as the processing and distribution center (P&DC) for post offices in a designated geographic area as defined by the first three digits of the ZIP Codes of those offices. Some SCFs serve more than one 3-digit ZIP Code range.

scheme sort

The distribution of mail to its destination according to a systematic plan determined by the mail processing functional area. Typically, this allows mailers to combine pieces addressed to two or more 3-digit ZIP Code areas.

Standard Mail

A class of mail consisting of mailable matter that is not mailed as First-Class Mail or entered as Periodicals. Standard Mail includes matter formerly classified as third-class and as fourth-class mail. Though combined in Standard Mail, matter from each former class remains subject to separate and specific classification, eligibility, and preparation standards. Matter formerly classified as third-class mail is referred to as Standard Mail (A); matter formerly classified as fourth-class mail is referred to as Standard Mail (B). The unmodified term Standard Mail applies to both former third-class mail and former fourth-class mail.

upgradable mail

First-Class Mail and Standard Mail that the USPS can process on a multiline optical character reader (MLOCR) to apply a barcode. Upgradable mail is letter-size, automation-compatible pieces, with machine-printed nonscript addresses, and OCR read area and a barcode clear zone meeting reflectance requirements, and paper that can accept ink. Preparation of upgradable pieces is usually simpler that the preparation of nonupgradable mail.

WKG (working)

A marking used on mail container labels that identifies the contents as mail requiring sorting and distribution.

Zip (Zone Improvement Plan) Code

Established in 1963, the system of 5-digit codes that identifies the individual post office or metropolitan area delivery station associated with an address. ZIP+4 is an enhanced code consisting of the 5-digit ZIP Code and four additional digits that identify a specific range of delivery addresses.

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