Tax Credits are part of the tax system.
They ARE being scrapped and replaced with a benefit.
There are big differences between UC and WTC, it's much more than just words.
For example, under UC, if you work part time and earn less than the equivalent of NMW full-time, then you will be expected to be looking for a full time job.
Thousands if people who work part time on low wages and currently get a top up, will start being treated as if they are unemployed. They will need to prove they're looking for work, just like people on JSA do now, and will be subject to conditionality - so if you don't do what the job centre says you lose your top up.
They could for example find you a dead-end job with more hours but no prospects, and effectively force you to give up the job you have to take it.
Under UC you will also find even more working people being sanctioned, resulting in homelessness or having to visit food banks to survive.