If we assume as given we'll eventually live in a society with a UBI (all eligible citizens receive an Unconditional Basic Income, enough to cover their food, clothing and shelter), then the most pressing question is: How should we roll it out?
Years of making Video Games suggest two quick answers:
The easy way is by lottery. Suppose Gary is a winner in the monthly UBI Lottery! Congrats Gary! Gary no longer has to deal with our mess of confusing taxation and welfare regulations. He wins a much simplified UBI and a flat tax. Of course, any change can be scary and difficult, so Gary also has the option to just stick with the old system if he wants.
More interesting is the notion of a Dual Currency. It's a little bit like enrolling in the food stamp program, where he's issued with tokens that can be exchanged for food items at a 1-1 ratio. In a food stamp program, those tokens would normally expire after a set period of time.
Food stamps are really old. Like, 1930's America old. We live in a digital world, so lets make those tokens work more like an energy mechanic in Candy Crush or League of Legends. Those tokens now accrue *continuously* rather than appearing all at once on a Thursday. We'll cap Gary's balance at a maximum of 1 months worth of tokens. Any balance more than 2 weeks of tokens would also have a penalty applied.
Finally pricing. Staples like bread, milk, laundry detergent and will have a heavily discounted price when purchased using tokens. Healthy options like fruit and vegetables too. Fast food and chocolates might have a premium pricing attached. Lets make it easier for Gary to make good decisions.