How to Write a Letter and Address an Envelope with the Correct US Postal Code

NEW YORK, NY 10001 is a real postal code for New York, New York. Where you place that code decides whether your letter reaches [recipient name] or lands in a dead‑letter bin.

Why the postal code position matters for sorting

The USPS uses machines that read the last line of the address block. That line must hold the city, state and ZIP code in that order. If the postal code sits anywhere else — say, on a separate line below the city — the machine may reject the letter. The optional ZIP+4 extension adds a hyphen and four more digits (99999‑9999) and narrows delivery to a specific building or floor.

The correct address layout

Write every address element on its own line. For mail sent inside the United States, omit the country line. The layout this site uses for the United States is:

  • Line 1: [recipient name]
  • Line 2: [street and house number]
  • Line 3: NEW YORK, NY 10001 (in capitals)
  • Line 4: UNITED STATES (in capitals, only for mail from abroad)

Capitalise the city, state abbreviation and postal code on line 3. Do not put a comma between the state and the ZIP code — just a space. For example: NEW YORK, NY 10001.

Step‑by‑step guide to write and send a letter

  1. Find the recipient’s postal code. Use the USAZip.Codes postal code search to look up the correct 5‑digit ZIP or ZIP+4 for the street address. Never guess the code.
  2. Write the letter. Start with the date and place: [date], [city]. Open with a greeting such as “Dear [name].” State the purpose in the first sentence. Keep the body clear and concise. Close with a formula like “Sincerely,” then sign and print your name.
  3. Draft the envelope address. Copy the recipient’s address in the layout above. For US‑only mail, omit line 4. For international mail, add UNITED STATES in capitals on the last line.
  4. Check your own return address. Write your name, street and house number, city, state and postal code in the top‑left corner. Use the same format but without the country line unless you mail from abroad.
  5. Review for common mistakes. Look for a missing ZIP code, a misplaced comma, or an abbreviation that is not the official two‑letter state code. If you used a ZIP+4, make sure the hyphen is present and the four extra digits are right.
  6. Post the letter. Affix postage (check current rates on the USPS site) and drop it in a mailbox or at a post office.

Tools for drafting and keeping the right length

If you struggle to start, use a askai.free AI chat to draft the letter with AI, then edit it yourself. For letters that need translation — for example, writing to someone who speaks another language — the askai.free AI translator can help convert your draft while you keep the address in English. After drafting, check the word count with a wordcounttool.com word and character counter, to keep the letter the right length. No official US letter has a required length, but most business letters stay under one page.

For the exact rules on address formatting — punctuation, abbreviation standards, and how to handle apartment numbers — refer to the USPS official addressing guide. If you send mail to or from other countries, the Universal Postal Union sets the international standards for address layout.