> how many of these cases do you miss because the recipients use a not easy traceable proxy entity to collect the payment?

That's the 'million dollar question', and in some cases substantially more than one million. I think the reason a good number of these people get caught is (1) things like the Panama papers and other leaks like that have made it harder to do this, and have also brought the not insubstantial resources of the authorities to review these constructs and (2) most people never expect that during DD such a thing would be checked.

It's typically quite a surprise when we start asking about the activities of companies that the other party believes are well hidden.