"I was looking for information about requirements in PA and IL."

Yes, that's why I pointed out it's unlikely a ProSeries peer user community can answer such specific details, without us doing your research. I gave a PA-specific link for your reference.

"And unfortunately, there is a whole list of things that should have been done in IL"

Yes, they are the worst, and I somehow became an IL sales tax go-to person when I started helping some clients in IL, and I'm in MT and we don't even have Sales Taxes!