[ejlo]

The tool for that is demurrage, http://en.wikipedia.org/wiki/Demurrage_%28currency%29, which adds devaluation of the currency over time. This complements Basic Income very well, with UBI for money creation and demurrage for money destruction.

For physical currency is has some obvious practical problems, which has prevent adoption, but for virtual currencies it is easy to implement.

[harperlee]

Well sorry, I did not explain myself properly: my idea was that, if every coin could be associated with a specific person, rich people's coins might devalue quicker than poor people's coins. It's a weird idea and giving it a little more thought, I don't see how could a state enforce such a system effectively, though.

[tlarkworthy]

variable Sales tax/VAT pegged to credit card and linked to SSN/NI

Cash purchases would be problematic. Maybe drawing out cash incurs the variable tax too?