A suite number in an address indicating that the business is in a building with other businesses located at the same address. The suite number helps direct the mail to the specific recipient for which it is intended. When addressing an envelope, the suite number goes on a specific line, but there is an exception, according to the United States Postal Service.

Write the street address with a comma after it, followed by the suite number on the same line. For example, "1234 Any St., Suite 321."

Write the suite number on the line above the street address if you can't fit it on the same line, according to the United States Postal Service.

Confirm that you have the correct street address and suite number before putting the letter or package in the mail.