What about this scenario. You purchase an item from ebay - it is packaged flat and sent as a large letter. You are charged $2 (which covers postage and packaging/envelope. The seller sticks 2 x 70c stamps on envelope (postage cost being $1.40). You would 'expect' to see an Australia Post receipt for this? What if the stamps were from a stamp booklet purchased months ago - and the seller removed the 2 stamps from that booklet to put on your article. How do they give you a receipt for this? They may if you are lucky have a receipt from the booklet purchase but not a receipt for sending your item because those stamps were prepurchased long ago. And what about the envelope, it may have come from a pack purchased from Officeworks - would you be expecting to see the sales receipt for the pack of envelopes/stationary that your envelope came from??