postalref

Mailer Identifier (MID)

The Mailer Identifier, or Mailer ID, is a field in Intelligent Mail barcodes that identifies the mailer. USPS assigns it as a 6-digit or 9-digit number, based on annual mail volume. Mailers print it in their barcodes and use it in eDoc to name the mail preparer and the mail owner.

Updated October 28, 202625 sources

What it is

A Mailer ID is a number USPS assigns to a mail owner, a mailing agent or another service provider that asks for one. Mailers use it in the Intelligent Mail barcodes for containers, trays, letters and flats, and packages.

Any business in the supply chain can own a Mailer ID. Each Mailer ID belongs to one Customer Registration ID, the number for a business location, at any given time.

The Mailer ID identifies the mailer in the barcode on the physical mail, and it names mail preparers and mail owners in eDoc. USPS also uses it to decide who receives mailing information and reports.

How it works

A business gets its first Mailer ID when it registers on the Business Customer Gateway. The Business Customer Gateway is the single entry point for USPS online business services, Mailer IDs among them. The system assigns a Customer Registration ID and a 9-digit Mailer ID when the account is created. Shippers who enroll in shipping programs on the Business Customer Gateway get one 9-digit master Mailer ID at the start.

A business that already has an account and needs another Mailer ID asks for it in the Mailer ID tool on the Business Customer Gateway.

Requesting a Mailer ID through the Business Customer Gateway.

  1. Log in to the Business Customer Gateway.
  2. Select the Mailing Services tab on the home page.
  3. Open the Mailer ID tool through its Go to Service link.
  4. Choose Request MID from the drop-down menu and follow the prompts.

Volume sets how many Mailer IDs a business can get. The first 9-digit Mailer ID needs no volume check. Each further 9-digit Mailer ID needs 1 million pieces of verified volume. Each 6-digit Mailer ID needs 10 million pieces, up to five in a request.

One request through the Mailer ID tool can ask for at most five 6-digit or ten 9-digit Mailer IDs.

Six or nine digits

The two lengths go to mailers of different sizes. A 6-digit Mailer ID goes to a mail owner or service provider with more than 10 million pieces a year. A 9-digit Mailer ID goes to one with less than 10 million pieces a year.

A 6-digit Mailer ID begins with a digit from 0 to 8. A 9-digit Mailer ID begins with 9.

A shorter Mailer ID leaves more room for the serial number. In an Intelligent Mail barcode, the serial number has 9 digits after a 6-digit Mailer ID and 6 digits after a 9-digit one. At certain volumes, a package mailer needs a 6-digit Mailer ID to keep serial numbers unique.

An eVS mailer has one master Mailer ID and may have several package Mailer IDs.

In a package barcode

In an Intelligent Mail package barcode, the channel identifier shows how long a commercial mailer's Mailer ID is. A commercial mailer with a 6-digit Mailer ID uses channel 93.

An illustrative package barcode from a commercial mailer with a 6-digit Mailer ID.

9312312345612345678906

The Mailer ID and serial number are examples.

The barcode, field by field
FieldDigitsMeaning
Channel9393 marks a commercial mailer with a 6-digit Mailer ID.A commercial mailer with a six-digit Mailer ID.
Service type code123Priority Mail: Open and Distribute (PMOD)
Mailer ID123456The number USPS assigned to the mailer.
Serial number1234567890
Check digit6
  • Passed22 digits: format C08, a six-digit Mailer ID and no ZIP.
  • PassedCheck digit 6 matches fields 3 to 6.
  • PassedThe six-digit Mailer ID starts with 1, as it must.
  • Passed123 is in Appendix I, effective 06/24/2026.

Requests by service providers

A mail service provider can request Mailer IDs for itself or for its customers. This service supports only 9-digit Mailer IDs. Its online form takes up to 10 requests at once. A CSV or Excel upload takes up to 100.

A provider that sends Mail.XML messages can also request 9-digit Mailer IDs that way. A provider cannot get a Mailer ID for a mail owner through new user registration.

A provider can look up a Mailer ID to see the Customer Registration ID and business address it belongs to.

The exception process

A mail owner that cannot get the number or length of Mailer IDs it needs in the Mailer ID tool uses the exception process. The request is in writing and gives the justification and how the Mailer IDs will be used. It includes at least these facts:

  • Total mailing volume per year.
  • The number of mailing locations.
  • Total volume per mailing location per year.
  • The mailing cycles at each location.

The exception process for a Mailer ID.

  1. The mailer submits the Mailer ID Application to a Business Mail Entry Unit or Mailpiece Design Analyst.
  2. The Business Mail Entry Unit or analyst checks the application is complete.
  3. They email the mailer's name and volume data to the PostalOne! Help Desk.
  4. The help desk adjusts the mailer's piece volume and notifies the customer.
  5. The mailer returns to the Mailer ID tool to obtain the Mailer ID.

USPS headquarters approves requests for more than the authorized number of Mailer IDs. A mailing agent can also use the application to request a Mailer ID for a mail owner. Both then sign section 3b of the form.

JACKPOT Mailer IDs

A JACKPOT CRID/MID is a shared identifier for small mail owners in a service provider's mailings. A provider whose mail owners each have fewer than 5,000 pieces, and who meets 90% Full-Service, may request one. It identifies only mail owners, never an eDoc submitter or a mail preparer.

The provider requests authorization by email to the Reconciliation Specialist team. Once approved, it names the account with its existing name preceded by JACKPOT. USPS audits every authorized mailer at random or as needed.

Rules

All IMbs produced by mailers must contain a valid Mailer ID (MID), except in the case where Origin IMb Tracing Services are desired (see 2.1.3 – D).

Every Intelligent Mail barcode a mailer produces must carry a valid Mailer ID. The one exception is a barcode for Origin IMb Tracing.

All mailers utilizing the new Intelligent Mail package barcode are required to use a conforming Mailer ID (MID).

A mailer that prints Intelligent Mail package barcodes must use a Mailer ID whose first digit matches its length.

When mailing agents make mailings on behalf of one or more clients (mail owners), they must request a unique Mailer ID (MID) for each client to designate package ownership.

A mailing agent that ships packages for clients must get a separate Mailer ID for each client. The Mailer ID shows who owns the package.

Mailers may not use a MID in their tracking barcodes for the Shipping Services File or in an IMpb until certification is complete

A mailer may not put a Mailer ID in a package barcode or a Shipping Services File before certification is complete.

A JACKPOT MID can never be used/printed within the IMb on a mailpiece, handling unit, or container placard.

A JACKPOT Mailer ID must never appear in a barcode on a mailpiece, a handling unit or a container placard. It belongs only in eDoc.

If the annual volume allows for more MIDs than these maximums allow, separate requests must be submitted.

A mailer whose volume earns more Mailer IDs than one request allows must submit more than one request.

Mail owners, mail preparers, and MSPs should note that MID/CRIDs are not available for use until 48 hours after Business Customer Gateway activation.

Mailers should expect a Mailer ID to be unusable for 48 hours after it is activated on the Business Customer Gateway.

What goes wrong

Using a Mailer ID too soon causes errors. eDoc finalized in PostalOne! within 48 hours of activation may generate electronic verification errors.

Wrong owner identification in eDoc logs By/For errors. Error 7140 means the mail owner and mail preparer are the same. Error 7142 means the mail owner was identified as a mail preparer in the past 90 days. A JACKPOT CRID/MID greatly reduces both errors.

A provider that misuses a JACKPOT CRID/MID may lose its authorization.

The PostalOne! Help Desk, a Business Mail Entry Unit or USPS headquarters verifies permit information through postal systems. When a system cannot verify the volume, a mailing agent can provide documentation instead.

Terms

Mailer IdentifierMID, Mailer IDs, Mailer Identification, Mailer Identification Number, USPS Mailer ID
MID is a unique 6- or 9-digit number that identifies the mailer or the mailer’s client.
Customer Registration IDCRID, Customer Registration Identification Number, Customer Registration Identifier, Customer Identifier, Customer Reference ID, Customer Registration Identifications
a USPS-generated numeric code of up to 15 digits that uniquely identifies a business at a specific location
Mail OwnerMO
the business entity, organization, or individual who makes business decisions regarding the mailpiece content, directly benefits from the mailing, and ultimately pays for the postage on the mailpiece directly or by way of a Mail Service Provider
Mail Service ProviderMSP, Mailing Service Providers, Mailing Agent
a business entity, organization, or individual acting on behalf of one or more Mail Owners by providing mailing services for which the Mail Owners compensate the Mail Service Provider.
Business Customer GatewayBCG, BCG (Business Customer Gateway)
where shippers can manage their mailing activity
Mailer ID ToolMailer ID system, MID system, MID tool, Business Customer Gateway Mailer ID system, Mailer ID service
The Mailer ID tool is the application on the Business Customer Gateway used by customers to obtain MIDs for use in either Confirmation Services or eVS programs.
Intelligent Mail BarcodeIMb, 4CB, Intelligent Mail barcode (piece level barcode), 4CB, 4-CB, USPS4CB, USPS 4-State Customer Barcode, 4-state customer barcode
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.
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.
Master MIDMaster Mailer Identification
The master MID is used for file transmissions from the eVS shipper and must be the MID used in the EFN submitted for all eVS files.
JACKPOT CRID/MID process
Mailers who choose to participate in the Jackpot CRID/MID process will see By/For errors (error codes 7140 and 7142) greatly reduced.

Documents

Publications

Quick Service Guides

Fact Sheets

FAQs

Applications/Forms

Contacts

For questions about Mailer IDs, call Intelligent Mail support at 1-800-522-9085 or email intelligentmailsupport@usps.gov. For Mailer IDs in package barcodes, the Package Services Customer Support Team answers at delivery.confirmation@usps.gov or 877-264-9693, Option 1. JACKPOT CRID/MID requests go to the Reconciliation Specialist team at recon@usps.gov.

Sources