How to write an address in Australia? What is the Australian postal address format? Addressing Your Letter 1. Seal your letter in an envelope. Fold the paper in thirds, horizontally, and slide it into the envelope. With dark ink, print their full name neatly in a. The second line should include the building number and street name. Write their street address directly below. If there is an apartment, suite or unit number, you can put it at the start of this line followed by a forward slash. If the delivery destination is an apartment, then the apartment number appears before then street number, with the number separated with a dash. Now write down the name or title of the person to whom you will be writing towards the centre of the envelope. In my case i am writing to a Principal of a school. Currently OCR’s used by Australia Post read the placename, State, postcode and other keywords from machine-addressed letters, and only the postcode from hand-addressed letters ...