Illinois recently enacted legislation requiring marketplace facilitators that meet certain thresholds to collect tax on behalf of their marketplace sellers. Marketplace facilitators must collect tax when they facilitate gross sales of $100,000 or more or when they facilitate 200 or more separate transactions for the sale of tangible personal property to purchasers in Illinois during the previous 12 months. This law goes into effect January 1, 2020.
A copy of the law can be found here.