Some of the biggest call-back operators have no operating licence, are not registered for business in Germany and decline to pay taxes on what they sell.
Ostensibly, a shift towards a gross profits tax relieves the operators of having to apply for Amusement Machine Licence Duty licences and having to account for VAT on their takings.
The scale of the undercharging became embarrassingly obvious last October, when two of the new licence-holders sold stakes to foreign operators prepared to pay handsomely for access to their spectrum.