Understanding the U.S. Address and ZIP Code System

If you're new to the U.S., even something as simple as writing an address can feel confusing. The format is the reverse of what most Koreans are used to — and with multiple ZIP code formats floating around, it's easy to make mistakes on important paperwork. Almost everything in American life, from opening a bank account to applying for a driver's license, starts with getting your address right.

How to Read and Write a U.S. Address

U.S. addresses go from smallest to largest unit. A typical address looks like this: 1234 Maple Street, Apt 5B, Los Angeles, CA 90210 — street number and name first, then the unit, city, two-letter state abbreviation, and ZIP code. A few things to keep in mind:

• The street number always comes before the street name — never after.
• Apartment or unit numbers are written as Apt, Unit, or Ste (Suite), either on a second address line or after a comma on the same line.
• State abbreviations are always two capital letters: CA, NY, TX, VA, GA, etc.
• A PO Box is a post office mailbox — it is not accepted as a residential address for a driver's license or REAL ID application.

ZIP Code vs. ZIP+4: What's the Difference?

The standard 5-digit ZIP code (e.g., 90210) identifies a general delivery area. The ZIP+4 code (e.g., 90210-1234) adds a four-digit suffix that narrows it down to a specific block or building. For everyday mail, the 5-digit ZIP is fine. But when mailing documents to the IRS or USCIS, using the full ZIP+4 reduces the chance of your mail getting lost or misrouted. You can look up your ZIP+4 for free at usps.com under "Look Up a ZIP Code."

Whenever you move, file a Change of Address with USPS — either online at usps.com or in person at your local post office. The online option costs just $1.10 (a small identity verification fee) and forwards your mail to the new address for up to 12 months. That said, USPS forwarding doesn't cover everything: you'll need to separately update your address with the SSA, your state DMV, your bank, and the IRS (using Form 8822). Don't skip those — missing a notice from any of these agencies can cause real headaches down the road.