The most common UBI variant is to simply give everyone the equivalent of a tax refund, no questions asked. Then, to pay for that, the tax rates at the higher income brackets go up.

Very low or zero income: the government pays you a basic income.

Low income: they still pay you, and you have to pay a negligible amount of tax on your extra income from work. Crucially, your benefits don’t disappear instantly if you get a job, unlike with many welfare programs now.

Mid-low income: you pay the same in taxes as the basic income, for a net tax rate of zero.

Higher incomes: your net tax after UBI increases proportionately to your income from work, steeper than before UBI.