In the dystopia I'm desperately trying to keep ahead of, nobody has actual money. It's a socialist paradise. Everyone has an embedded chip which carries, along with personal data and lots of other stuff, their bank balance. Nobody appears to pay income tax - in fact, tax is deducted before you're paid but nobody knows at what rate because all they see is the final amount they get. Nobody knows their pre-tax salary.
So there is absolute control over every transaction and tax on every transaction. How much tax? Nobody knows. An amount is deducted from the buyer's balance and a smaller amount is added to the seller's balance but at no point is the tax amount declared. Neither party knows the actual price, you just buy things, and you are required to explain yourself if you are not buying things because you are hampering the economy. Even if you sell stuff via the fictional equivalent of eBay, the transaction must be electronic and the bid you see on your screen isn't quite what the buyer sees on his. Emails passed between seller and buyer are auto-edited on the way.
How to make this happen? First you ban cash. Then cheques (I know, they started with the wrong one here) so everything is done via a credit card. These already have chips, and already can be integrated into phones. It's only a tiny step to integrate them into your implanted ID chip and just look how convenient it is. You can't lose it, you can't go right round the supermarket and then find you've left your card at home, and it can't be stolen. Perfect. People will fight each other to be the first to get this.
That's the fiction. I wondered how to go about banning cash from this imaginary world. What pretext could I use?
Ah, here it is. Once again, life is ahead of me.
You know, I've been wondering about all those maniacs stealing live cables and why it's so difficult to find scrapyards dealing in large amounts of copper wire.
Louisiana has made excellent use of those metal thieves. How long before we do, I wonder?
Best get back to writing.