Apologies for posting again and please do not get irritated... but I give up. I did try to find this info by myself, but after checking 3 different tax calculators and some gov websites I got only more confused. That's why I'd appreciate your advice.

My prospective employer, for the net income estimation, used for income tax the rate of 18.3% (Basel-Stadt). Does anybody know whether 18.3% represents sum of all 3 taxes (federal, cantonal, municipal) or maybe only 1 or 2 of them? I'm trying to figure out how much tax in total I'd have to pay and cannot figure out whether it's going to be 18.3% or 18.3% + something else...

Big thanks in advance!

It's all 3, or should be.
It'll be Quellenstuer (or direct/source tax) if you're on L and B permits.
The breakdown only happens later on, say if you fill in a tax return.