[euix]

I can't believe in a lot of these countries this is enforced or obeyed to any degree. The closer the empire is to collapse the stupider the laws.

[xxs]

The laws are there due to anti-money laundering. Since virtually no cash income (in those country) is viable - think salaries, etc., it's not hard to be followed. All retail sales need a valid VAT receipt, all of those receipts have source of the payment as well. Wholesale tends to be never in cash (requires tax administration approval), the laws might differ, of course - however that's a common framework.

So it's sort of automatic.