I wonder if there are differences as to what is ‘normal’ in different parts of Spain.
I’ve been in Andalucia so you can imagine that for me cash in hand, underdeclaring, corrupt Mayors, buildings without licences etc. etc.etc is 100% perfectly day to day normality!
What about though in say Barcelona, or Madrid? I think that paying a builder or plumber in Andalucia with anything other than cash would get you a bit of a kicking but in cities?
Try it then Rocker, ask for a bill. I can imagine a scrunched up napkin from a local tapas bar with some numbers scribbled on it being handed over 😉