Hello.
Not sure if this is known to people, but wanted to share my experience.
I purchased mk4 kit (no tax collected) in 2017. Finished build in 2018.
Submitted paperwork for title and registration couple weeks ago. Well today I got a letter from IRS that I need to pay a late filling fee plus daily interest.
Not a huge deal, couple hundred bucks, but still suprise.
Don't delay your sales tax, at least in Illinois.