It depends on what the starting point is. In Denmark every single person have tax deduction. For persons over 18 that is currently 46.000 DKK. In addition there is a host of other deductions and benefits for various situations. UBI would replace some/many of those, so it would in essence be a tax reform. It still doesn't capture the majority of economic activity the state is involved in, but it would make a lot of things significantly simpler.