It can be structured as an income tax that starts out negative. Everyone of working age is paid the UBI, which is designed to act as the safety net. This frees up a ton of overhead as means-testing, benefit fraud, etc. all goes away.

Then when you get a job, the UBI starts to reduce, at a rate LESS than the money you are earning. So if you're paid $1000 monthly UBI, and get a $1000 job, it might reduce UBI by $500. So you're always better off working. You'd probably want a sliding scale so maybe the first couple of hundred only reduces your UBI by 0.20 per dollar, or whatever. It can be structured so the net tax take for the government is the same. Yes this probably means people earning more than say $100,000 pay a bit more in tax. I'm okay with that.