USPS Address Guidelines
Jan 25, 2024

USPS Address Guidelines

The delivery address is the most important information on a mailpiece. Almost 25% of all mailpieces include a mistake in the address, such as a missing apartment number or a wrong ZIP Code. These mailpieces can still be delivered, however, it may cost the Postal Service time and resources.

Required Addressing Details

The USPS postal addressing standards say a full address consists of only three lines as follows:

  • Recipient Line
  • Delivery Address Line (Street address)
  • Last Line (City, State ZIP code)

For example:

Philip Gaillard
7650 Tallwood Street
Gainesville, VA 20155

Secondary Address Unit Designator

Secondary address unit designators, such as APARTMENT or SUITE, are required and are recommended to be included in the Delivery Address Line (second line). These designators are:

  • Apartment – APT
  • Building – BLDG
  • Floor – FL
  • Suite – STE
  • Room – RM
  • Department – DEPT
  • Unit – Unit (no abbreviation)

USPS advises that when the apartment number doesn’t fit on the street address line, it should be written ABOVE the street information. The USPS prefers including the apartment number on one long street address line, but also suggests the alternative of including an apt line above the street address.

Using the pound sign in your apartment address

The pound sign (#) should not be used as a secondary unit designator if the correct designation, such as APT or STE, is known or is shown in the ZIP+4 file. If the pound sign (#) is used, there must be a space between the pound sign and the secondary number.


Directionals are part of the address that gives directional information for delivery (i.e., N, S, E, W, NE, NW, SE, SW). They are very important to include in an address. A missing or a bad directional can prevent your mail from being delivered correctly. This could also mean your package could end up on the wrong side of town, as many cities have two different streets with the same name.

Post Office Box Addresses

The Post Office Box address on a mailpiece must be standardized as follows: PO BOX


  • On a letter, the address should be parallel to the longest side.
  • All capital letters.
  • No punctuation.
  • At least 10-point type.
  • Simple type fonts.
  • Left justified.
  • Black ink on white or light paper.
  • No reverse type (white printing on a black background).
  • Always put the address and the postage on the same side of your mailpiece
  • One space between city and state.
  • Two spaces between state and ZIP Code.

If you are using address labels, make sure you don't cut off any important information. Also, make sure your labels are on straight. Mail processing machines have trouble reading crooked or slanted information.

What Makes an Address Valid?

A valid US address typically contains the following elements:

  1. Street address: This includes the house number and street name.
  2. City: This is the name of the city or town where the address is located.
  3. State: This is the two-letter abbreviation of the state where the address is located.
  4. ZIP code: This is a five- or nine-digit code that identifies the specific geographic location of the address.
  5. Country: In the US, this is typically listed as "United States" or simply "US."

For a US address to be considered valid, it must contain all of these elements and accurately reflect the actual location of the address. Additionally, it is important to use the correct format for each element when entering an address, such as using proper abbreviations and avoiding typos.

Address Validation

If you require assistance on completing a US address, you can input part of the address details into our Address lookup demo.