How will they enforce it? I'm sure big/medium businesses will comply, but how can you track a cash transaction between private citizens?

Furthermore in the country where I live (Italy, one of EU founding members) more than 60% of independent professionals (partite iva) evade/elude taxes in some way or another, and it's very common (so common that every Italian experienced it many times in their lives, me included) for small businesses and professionals to offer you a slight discount if you pay cash under the table (no receipt, so no taxes) and, even if we have an entire police force dedicated to financial crimes, the submerged economy is just so big that they can't deal with it now, imagine when they'll have to arrest/fine everybody that accepts more than €3000 in cash.

What somebody writes on a piece of paper and what happens in the real world are 2 very distinct things, many stores in Italy don't accept credit cards even if it's against them law, and only a minuscule fraction of them gets fined.

The EU has extremely nazi-esque control on the private financial life of its citizens (the state monitors your bank account, to open a bank account you need to give every info about u in the future they'll ask for your DNA probably, if you withdraw/deposit a "suspect" amount of money our IRS will come after your ass, ane you need to prove your innocence basically guilty untill proven otherwise, ecc, there are a thousand examples, I'm sure EU citizens can relate) but I can't see how they'll be able to track pieces of paper.

TLDR I can't even see how they will be able to enforce this law, especially when we talk about small businesses/independent contractors, and the situation gets even funnier when its a transaction between 2 private individuals.