How do I format a ZIP+4 code?

Five digits, hyphen, four digits (e.g., 12345-6789). Use the hyphen when writing the full 9-digit code.

Is ZIP+4 required for mail delivery?

No. ZIP+4 is optional for most mail, but it can improve automation, sorting, and accuracy—especially for high-density or business addresses.

Where can I find my ZIP+4 code?

Use the official USPS ZIP Code Lookup, check recent mail that includes your full address, or ask your local post office.

ZIP+4 Code Format Guide: How to Use 9-Digit ZIP Codes

Q: What is a ZIP+4 code?

A ZIP+4 code is a 9-digit postal code: the standard 5-digit ZIP plus a 4-digit add-on that narrows delivery to a specific route, building, or segment.

The ZIP+4 add-on can speed automated sorting and improve accuracy. Here’s how the format works, when it helps, and where to look it up.

Example of a 9-digit ZIP+4 code with hyphen separator — Visual example of the ZIP+4 code structure with a hyphen between the 5-digit ZIP and 4-digit add-on.

What is a ZIP+4 Code?

A ZIP+4 code is the 5-digit ZIP plus a 4-digit add-on that narrows delivery to a sector/segment within the ZIP. It supports USPS automation and routing but is not required for most mail.

ZIP+4 Format

12345-6789

Five digits, hyphen, four digits. Use the hyphen when writing the full 9-digit code.

Benefits of Using ZIP+4

Improves automated sorting and routing
Reduces misdelivery risk in high-density addresses
Can speed processing for business/volume mail

How to Find ZIP+4 Codes

Official USPS Lookup

Enter a full street address (including unit/floor if applicable) to get the precise ZIP+4.

Open USPS ZIP Code Lookup

Note: the tool returns addresses in USPS-standardized format.

Check Existing Mail

Statements and government or business mail often include your full ZIP+4.

Proper ZIP+4 Formatting (USPS Style)

✅ Correct

MS MILDRED DOE

12 E BUSINESS LN STE 209

ANYTOWN NY 10001-1234

Uppercase city/state line; two-letter state
Hyphen between ZIP and +4; no spaces around the hyphen

Based on USPS Publication 28 addressing standards.

❌ Incorrect

Ms. Mildred Doe

12 East Business Lane Suite 209

AnyTown, New York 100011234

Mixed case and punctuation on last line
Missing hyphen in ZIP+4

When to Use ZIP+4

High-density delivery points (apartments, offices, campuses)
Business/volume mail where automation matters
Time-sensitive or important correspondence

ZIP+4 vs 5-Digit ZIP

Comparison of ZIP+4 codes versus regular 5-digit ZIP codes
Feature	5-Digit ZIP	ZIP+4
Precision	General area	Specific sector/segment
Processing	Standard	Better automation
Required?	Yes (use at least 5 digits)	Optional but recommended