black market purchase

基本解释

The fact is that large numbers of illegal immigrants already pay payroll taxes, and there is no reason to believe that the ones who have decided to offer their labor on the black market would not decide to purchase goods on the black market as well.
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This action targets those people that have been using credit cards as a way to purchase at the official rate rather than the black market rate, in effect creating a dual credit card exchange regime.
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