A new postal regulation is now in effect pertaining to the placement of the address label on all "flat size" mail.

Flat size mail is described as any envelope, brochure or booklet more than 6" high or more than 11" long. The address must be placed in the top half of a portrait orientation booklet or the right half of a large envelope.

Download a PDF document for addresing large envelopes
Download a PDF document for addresing brochures and booklets
Flats design fact sheet

Dimensions of a "Flat":

flat dimensions