For several years (up until a year ago) I was unemployed most of the time but with occasional casual work. Every time I got such work (as well as signing off the dole) I had to write to the Council Tax people to tell them about my change of circumstances and then, a few days later (when the work had ended) I had to write to them again to tell them that I'd 'signed on' again. Every time I did that (which could sometimes be two or three times in a month) they required me to go to my bank, get a complete print-out of all my last 6 months transactions (which had to be stamped and signed by the bank's cashier) and then submit it to them. So they were certainly determined to check up on how much I'd got in the bank and how much income I had coming in!