Parsing the Structure of US Addresses

Parsing the Structure of US Addresses

A US address separates the street location from the city, state and ZIP Code. Knowing those parts helps you preserve the recipient’s information when completing a form. Correct formatting alone does not establish that an address exists or can receive a delivery.

I. The Four Core Components

For a standard mailpiece, USPS distinguishes the delivery address line from the last line containing the city, state and ZIP Code. Website fields can split those parts differently. See Publication 28, section 211.

1. Street information

   • Keep the house number, street name, applicable directional and street suffix from the recipient’s address.
   • Directionals can appear before or after the street name and suffix. Do not move or invent one; section 233 distinguishes these cases.
   • For a mailpiece, the preferred place for an apartment or suite is at the end of the delivery address line. If it will not fit, put the secondary information immediately above that line. This USPS rule is not a rule that every website’s second field prints as the second line.

2. City

   • Use the mailing city name associated with the address. USPS recommends an approved last-line name from its current City State file; a municipal boundary alone does not determine the mailing name. See section 221.

3. State

   • Keep the state separate from the city. Standard postal abbreviations include CA for California and TX for Texas; use the form’s supported selection or code.

4. ZIP Code

   • A ZIP Code has five digits; ZIP+4 adds a hyphen and four more digits. Use the code belonging to the complete address, rather than guessing from the state or a nearby address.
   • Store it as text so leading zeros survive. See the ZIP Code and CSV guide.

II. Special Address Types

• PO Box: a postal box number is not a street apartment. Use the recipient’s actual box details; the PO Box and street address guide explains the difference.
• Military and diplomatic mail: APO, FPO and DPO follow their own city/state conventions. Follow the APO/FPO/DPO guide rather than replacing those fields with a foreign city.
• Buildings and units: retain identifiers supplied by the recipient. BLDG, APT, STE and UNIT are different designators, not interchangeable labels. A sample such as STE 200 illustrates syntax only; it does not identify a verified delivery location.

III. Formatting and Validation Are Different

CASS is a USPS program for evaluating address-matching software. It is not proof that any randomly generated address is deliverable, and this page does not claim USAddressGen is CASS-certified.

LACSLink uses address-conversion records, including changes associated with 911 addressing and street renaming or renumbering. Its scope does not mean that any incomplete rural address can be repaired automatically.

For unit designators, use the known type, such as APT or STE. The # symbol is not universally forbidden: USPS requires a space before the following number when it is used, and has separate rules for private mailbox addresses. Consult section 213 and Appendix C2; do not guess a unit number.

IV. Use Generated Addresses as Test Data

The USAddressGen tool can help exercise address fields, saved records and exports. Keep the parts of each sample together and distinguish testing from an actual shipment. The tool does not provide a receiving address, proof of residence or a guarantee of third-party account verification.

For a real delivery, use the recipient’s complete address and the postal service or carrier’s validation process. The official references above were checked on October 22, 2026; no delivery or third-party form test was performed.