Here's something not a lot of people know; it really doesn't matter where you put a stamp on an envelope, at least in the United States. While stamps help you conveniently ship items using the postal service, there aren't any regulations on stamp placement. Your mail will get to its location regardless of where you slap the stamp on the envelope, according to USPS mail carriers Jennifer Chacos and Carlos Rodgers. That being said, there is a conventional area to place stamps on mail, and the automated sorting machines used by the United States Postal Service orient themselves to this location. Your mail will need to be hand-sorted if you place your stamps anywhere else, which slows its delivery time.
Flip the envelope to its front side. Look for a solid sheet of paper -- the rear side has an opening flap for slipping contents inside the envelope.
Locate the upper right-hand corner of the envelope's front side. The flap on the rear of the envelope opens at the top -- orient the envelope and find the upper right corner using that as a reference point.
Affix the appropriate number of stamps to the upper right-hand corner. The number of stamps needed depends on the weight of the envelope or package -- use the U.S. Postal Service's online rate calculator or its price list to determine how many stamps are needed. Place multiple stamps next to each another and avoid overlapping or covering one stamp with another.
Place stamps in the upper right corner of packages in the same manner you would for an envelope.