I know once I went to PO to get something weighed ahead of time B/C I was going to put the stamps on it when I got home and when I brought it back the next day to mail it, she re-weighed it and said I owed 70+ cents more. I said what?! You just weighed it yesterday for me and I put the correct amt of stamps on it! She asked did I add something new, NO, I said, just a little note and THAT couldn't possibly be it. So I opened my pkg to show her and she weighed again w/o the note and sure enough, it was what she had previously quoted. So heads up people....just adding a SMALL little note will ADD lots to your previous cost! I was shocked at the difference, so I always go once and that's to mail it so it will be totally correct when they weigh it just ONCE! But I do use the flat rate bubble envelopes now anyway and those you do have to order online.