There's no guarantee the utility bill stuff will work, but it's another hoop for them to jump through and it works in that sense. I ask for that, a deposit if the travel time is ridiculous, on top of the regular stuff like a phonecall beforehand and checking their number. I don't even bother asking for landline number anymore as next to nobody has one these days and it's just a faff, I like the utility bill method a fair bit more. Haven't had any problems, have had clients not come back to me about it but as if I give a shit. I'm not full-time and can easily live on one outcall a week or a fortnight, but I get much more than that (not that I can be bothered to work that often during term time). It's all about the hoops and gut instinct too - The more suspicious I am, the more hoops to jump through.