Well yes, in the sense that Al Capone famously got nailed on not filing income taxes. But of course, if Al Capone had told the IRS that he got his money through

Well yes, in the sense that Al Capone famously got nailed on not filing income taxes. But of course, if Al Capone had told the IRS that he got his money through extortion and illegal liquor, gambling and drugs or whatever it was he did then the IRS would gladly give that information to whoever was investigating him, so I don't think the IRS would profit much from it either way. And I imagine card payments do make it harder, but the schemes just become more difficult, which might press on the margins a little. You could always buy your kebab shops overseas. Sell your drugs for Bitcoin, send the Bitcoin to Berlin, exchange them there for Euros, cash them in at your Kebab shop, and then wire them back to New Zealand, bam you're an international investor in the eyes of your government.