I guess what concerns me whether other than German governments are already known to employ that procedure where they contact end clients and possibly agencies for the sole purpose of tracking down IT contractors. This is the gotcha when the government stars talking directly to end-clients.
Lets face it if Germany is doing it, sooner or later every other government will try to do it, they just need to catch up technologically and organizationally. Which to some other EU countries may mean 20 - 40 years .... maybe less. I am not sure where the mid-level countries : Belgium/Netherlands/Scandinavians/etc stand on this re tracking down IT contractors.
I am aware of more and more EU countries's Revenue Agencies getting technologically connected to the corresponding agencies in other countries for the purpose of exchanging information on who worked where. That is to track who paid taxes where.
So these investigations are only beginning to ramp up. Soon there may be no place to hide. And if then they ask your son to pick up a gun and go to war with someone. Tell him "sorry son, I had go along with it all".
And please don't use the word taxman. I don't see anything masculine about this system.