My god there are some honest people on here!
I think the tax man is fully aware that people in jobs like ours that handle plenty of cash don't always declare 100% of it, but we are small potatoes, the average window cleaner banks less than 20k per year.
Most of us bank most of our money, we have to, we won't get by otherwise.
do you really think the tax man is that stupid?
If you assume that most of us are pretty honest - and most of us are - then if the tax man decides to investigate one of us he might only find a few hundred quids worth of discrepancies, and much time and effort will have gone into doing so.
Far better in investigate businesses who aren't such pipsqueaks.
They will view small businesses as those who employ 30 or 40 people, probably all of which earn more than the average window cleaner banks in an entire year! Their time and effort chasing down tax dodgers of this size (and of course far larger) represents a far better return for their time and effort, way better than chasing down the many thousands of individual window cleaners, gardeners, hair dressers, decorators and the like.
They could probably pull almost any one of our files and find discrepancies if they wanted to...
Ian