Do you need to have a zip code to mail a letter?

ZIP Codes are required on Express Mail, commercial First-Class

Mail,

First-Class

Package Service, Periodicals, Standard Mail, Package Services and Parcel Select mailpieces,

all mail sent to military addresses within the United States and to APO and FPO addresses, official mail, Business Reply Mail, and merchandise return service mail.

Unless required above, ZIP Codes may be omitted from single-piece

price

First-Class

Mail (including Priority Mail), single-piece

price Standard Post, and pieces bearing a simplified address.