i will be the oddball here and say that I dont have my customers sign the invoice. At the beginning of the job we walk through the area to be cleaned, I measure it up and as I hand it to them, I say *and here is your receipt. Lets make sure I have it down right* and then go through the slip line by line. then ask if they have any questions and then go do the work. I do high end residential and never thought a signature would make any difference and for over 35+ years never had a problem doing it this way.