USPS Address Formatting and Requirements

Getting Started

Ensuring your recipient addresses are well-formatted and accurate helps improve deliverability and avoid delays. Whether you're prepping just one address or an entire mailing list, this guide walks you through best practices and tools to make your mailings succeed.

Why Proper Formatting Matters

Correctly formatted and verified addresses reduce errors and support faster, more accurate delivery. Using tools like USPS validation or our cleanup services helps ensure every address conforms to postal standards.

Address Verification Tools

LetterStream’s Address Cleanup Tools when using CSV files for larger mailings
USPS Address Verification Tool
Google Maps or similar for confirming address accuracy

These tools help identify misspelled city names, missing zip codes, or incorrect formatting before mailing.

Minimum Required Fields

Every mailing must include:

Recipient Name
Street Address
City, State, and ZIP Code

Without these elements, USPS may not be able to deliver your mail.

USPS Address Formatting Guidelines

For best results, follow these preferred formatting rules:

Use ALL UPPERCASE letters
Avoid periods and commas
Abbreviate as follows:
- Street Directions: N, S, E, W
- Street Types: ST, AVE, RD, BLVD, DR, LN, etc.
- Unit Types: APT, STE, RM, BLDG, DEPT, FL, etc.
Use a space after the number sign (#) before the unit number
Avoid mixing P.O. Box and street addresses
A full 9-digit ZIP code (ZIP+4) is preferred if available
Do not use city abbreviations

The USPS is still able to deliver your letters without these items being adhered to perfectly, though this can increase deliverability.

Using Company and Additional Address Lines

LetterStream supports up to 5 address lines, best used like this:

5-Line Format (Optional)

LETTERSTREAM, INC.
ATTN: SAMPLE NAME
8551 E ANDERSON DR
SUITE 108
SCOTTSDALE AZ 85255

Compact 4-Line (Recommended)

LETTERSTREAM, INC.
ATTN: SAMPLE NAME
8551 E ANDERSON DR, SUITE 108
SCOTTSDALE AZ 85255

Use the second name line for company or attention details
We don't recommend putting someone's last name only in the second name field
If needed, you can use a second address line for unit details like suites or apartments, though we recommend only using one address line
Avoid extra lines unless necessary — simplicity helps improve readability and processing

Understanding Street Address Components

Use this framework when formatting addresses:

House/Street Number (e.g., 123)
Street Direction (e.g., N, S)
Street Name (e.g., MAIN)
Street Type (e.g., ST, LN, RD)

Formatted example:

123 E MAIN ST

These parts help clearly distinguish the delivery location, aiding USPS and emergency personnel alike.

For an example of a properly formatted CSV file, click here.