A few years back I was doing a minor alteration on the family home. One of the builders who I got in to do a quote gave me his price and then said “but if you can pay cash it will be $X” (a figure about 13% lower than his first quote). I didn’t hire him, even though I could have saved a nice chunk of change. I figured that if he was dishonest enough to defraud the government, what would stop him from trying to do the dirty on me as well. And with no records of the transaction, I would have nothing to fall back on.