ZIP Code™ - The Basics

Why are ZIP Codes™ necessary?

Mailpieces with a ZIP Code are processed quickly and efficiently. Alleviates possible delays due to manual handling. 

What are the parts of a ZIP™ Code?

The nine digits of a ZIP+4 code (e.g.,12345-6789) may be grouped as follows: [123] [45] [67] [89]

• [123] :  Sectional Center or Large City
• [45] : Post Office facility or Delivery Area
• [ - ] : The required "dash" or "hyphen" separates the first five digits from the last four digits; the +4
• [67] : Sector or Several Blocks
• [89] : Segment or One Side of a Street

Is the hyphen in a ZIP+4® ZIP Code™ number required?

Yes, when using a ZIP+4 ZIP Code, the number must consist of five digits, a hyphen (or dash), and four digits. Improperly labeled mailpieces may progress slower through the mail system and may be returned to sender if the United States Postal Service® is unable to deliver the item.

ZIP Code History

Visit: website Publication 100 - The United States Postal Service - An American History 1775 - 2006  for History of the United States Postal Service®

Are ZIP Codes™ 5-digit or ZIP+4 required?

Required in the return address of all mail on which postage is paid with precanceled stamps or company permit imprint, and in the sender's return address on Periodicals mail when "Address Service Requested" is specified. 

Official mail (penalty mail) also requires a ZIP Code™ in the return address.

Can I access a database or directory of all ZIP Code™, ZIP+4 and Post Office™?

This valuable information is now available in the Address Information System Viewer (AIS). The AIS Viewer is an interactive application designed to provide the ability to retrieve, view, and print accurate and current ZIP Code information for all 50 states on request.

More information on the AIS View, go to https://postalpro.usps.com/address-quality/ais-viewer or call the National Customer Support Center at 1-800-238-3150 and select “Option 6” followed by “Option 2” to speak with a customer service representative.

What is a ZIP Code™ or ZIP+4® Status / Type?

Note: City names should be completely and legibly written out to help the Postal Service process and deliver items more efficiently. 

"Status" Definitions:

• Acceptable: Status of Acceptable (Default) means an adequate city name has been entered or received based on information entered. City names that are abbreviated will frequently be listed as unacceptable because abbreviations are not an acceptable city name format.   

• Not Acceptable (or Unacceptable): Means an inadequate city name has been entered or received based on information entered.

• Unique: Assigned to a company, government agency, or entity with sufficient mail volume, based on average daily volume of letter size mail received, availability of ZIP Code numbers in the postal area, and USPS cost-benefit analysis. 

"Type" Definition:

Standard: It is the established and usual ZIP Code used in a specified area.

How do I get a Unique ZIP+4®?

The ZIP+4® Code assigned by the Postal Service™ is unique for the category of Reply Mail you use.  This unique ZIP+4 code enables Reply Mail to be sorted on postal automated equipment by specific size and weight (i.e., cards, 1oz. letters, 2 oz. letters, etc.).

1. Register your company and authorized users using Customer Registration.
2. Select the “Add ZIP+4 Code” option within the online Business Reply Mail (BRM) tool (accessible after clicking "Automated Business Reply Mail" upon logging on to the Business Customer Gateway).
3. Select the media type that you intend to use.
4. Provide complete delivery information for the BRM mailpieces that will be returned.
5. Submit your request.
6. The standardized delivery information (with the assigned unique ZIP+4®) will be sent to you for use on your mail piece. 

Will a ZIP Code™ or ZIP+4® for a PO Box™ change?

ZIP Codes for PO Boxes within the same city usually do not change. Please note that the ZIP+4 Code will likely include the actual PO Box number in the +4 part of the ZIP Code.

For further information on how ZIP Codes are assigned to PO Boxes, please contact your local Post Office™. 

Concern

Action

Solution

Street name is misspelled in the ZIP Code™ or ZIP+4® Look-up tool on usps.com.

How can this problem be fixed?

Contact your local Post Office and request their assistance in resolving the problem. All information in our national ZIP Code database is maintained by the Address Management System (AMS) Office and request the street name to be corrected.

The ZIP Code™ or ZIP+4® where I live changed recently.

Due to an increase in population or to the improve postal operations, the US Postal Service® will occasionally add a new ZIP Code or change ZIP Code boundaries.

ZIP Code lookup on USPS.com not showing this change?

The reason why a change isn’t showing may be the national site hasn’t been updated yet by the local Address Management System (AMS) office.  Any changes, corrections, or updates to the national database will be reflected in the ZIP Code lookup tool on USPS.com within 30 to 60 days. 

Where can I find an international/foreign ZIP Code™(Postal Code)?

The U.S. Postal Service® does not keep information on Foreign Postal Codes (similar to the ZIP Code used in the USA).

For the Postal Service to deliver mail to a foreign country, we only need the name of the destination country. For postal code information for a foreign country, it is recommended that you contact the country in question or look for further information about that country's postal codes on the internet.

Why will the ZIP Code™ Look-up tool not acknowledge the address that I entered?

Address may have been entered incorrectly, is an invalid address, or it may be a new construction address or a new housing development.  Verify that the address you have is correct.

Enter it in the ZIP Code™ lookup tool.

If you still do not get a response and the address is a valid mailing address, contact the local Post Office and request their assistance in resolving the problem.

ZIP Code™ or ZIP+4® does not match City/State.

In cases where mail has a street / city / state of one place but the ZIP Code™ area does not match, it is difficult to determine which Post Office™ is the actual office of destination.

The U.S Postal Service® dispatches mail sent in this manner to the Post Office indicated by the ZIP Code for possible delivery.

If undeliverable there, it is forwarded to the Post Office as stated by city and state.