1. Those that are currently illegal: The intention if that you DON'T pay for those any more. 2. Those which are "taboo". You bank/card statement is something private; it's not gonna be public (they aren't not either). If you pay for sexual services, most likely (a) Whomever you pay would probably have a non-obvious name for bank statements, (b) Should keep records private. As it is today, if that person wants to blackmail you collecting evidence, they still can.
Would be trivial to accept and process these payments.
Another avenue might be some kind of mutual fund. A building society for the grey market. One where your paper trail would tie you to a fund used for illicit goods, but not directly to your particular flavour of illicit good. That'd require a great deal more work though... And comes with the obvious risks.
Final thought there's always replacing cash. After all cash is just paper we all agree has value. If the underground markets can find a similar good with similarly agreed value that might work. I've heard of phone scammers requesting their mark's buy gift cards/vouchers. Presumably they're monetizing the voucher on their end somehow.
The goal of a cashless society seems to be more in line with the even greater transparent creation of money. These "we can track criminal financiers!" soundbytes sound more like the cursory glance reason you'd give the public.
Largely cashless societies recently seem to have either been deeply entrenched in the financial industry, or rife with wider corruption. Both of those will want to continue in a clandestine manner. The law might not apply to the rich, but you can bet you'll be slapped down for not at least trying to hide it. I can't imagine a system cashless or otherwise that didn't have at least some mechanism to move wealth without fanfare.
Utopia - a fictional concept where, yes, you can have 100% law abiding citizens.
> is a utopia where money cannot leave – or even exist – outside the banking system, but can only be transferred from bank to bank.
How do people in a cashless economy pay for stuff that demands discretion, and that which they don't want documented or traced back to them?
Example: Buying weed or drugs or underage alcohol, maintaining mistresses or paying for sexual services or anything else that is either a social taboo or is downright illegal? Are you telling me that everyone in Sweden is a 100% law abiding, obedient 'good' citizen and hence they don't have a need to be able to transact from time to time using a relatively discreet currency = cash ?