It is important that this is based on all income levels equally. Yes, some will pay back that money in taxes, but the important part is keeping the amount equal. It would be even more effective if you gave them a monthly check (even if you would eventually take it all back via a consumption tax on people earning more). A ~25% national sales tax should be sufficient to cover a UBI program. (We should still have an income tax, though.) Furthermore, a consumption tax would decrease unnecessary spending since you can target only new products and not used products to encourage people to reduce, reuse, and recycle.
If UBI is encoded as a negative tax rate at low income levels, it no longer really makes sense to talk about it as applying to all income levels equally. It naturally gets distributed as
1) A check (issued by Social Security service?) if income is less than X
2) Less of your paycheck being withheld if your income is greater than X (or more if you're significantly above X, depending on how this gets funded)
