The premise of an actual UBI is that it's universal, i.e. unconditional. If the UBI is $12,000/year then everybody gets $12,000 a year. If you don't have a job then you get $12,000. If you have a job that pays $10,000/year then you get $12,000 plus that $10,000. If you have a job that pays $100,000/year then you get $12,000 plus that $100,000.
Of course, you also pay taxes out of whatever you make, so the person who makes $100,000 might be paying $30,000 in taxes and then they're effectively paying $18,000 rather than receiving $12,000. But that's fine and is actually want you want, because it produces a progressive rate curve even when everyone is paying the same marginal tax rate. Right now we put irrationally high marginal rates on lower and middle income people in the form of benefits phase outs. With a UBI they get the benefits as cash and experience the phase outs as paying taxes at the same (rather than a higher) marginal rate as higher income people.
You don't want people doing nothing. You want them to have the incentive to take productive employment when it's available. Taking away the money you give them because they take a job is exactly what you don't want, which is crazy.
Of course, you also pay taxes out of whatever you make, so the person who makes $100,000 might be paying $30,000 in taxes and then they're effectively paying $18,000 rather than receiving $12,000. But that's fine and is actually want you want, because it produces a progressive rate curve even when everyone is paying the same marginal tax rate. Right now we put irrationally high marginal rates on lower and middle income people in the form of benefits phase outs. With a UBI they get the benefits as cash and experience the phase outs as paying taxes at the same (rather than a higher) marginal rate as higher income people.
You don't want people doing nothing. You want them to have the incentive to take productive employment when it's available. Taking away the money you give them because they take a job is exactly what you don't want, which is crazy.