The Illinois Department of Revenue (IDOR) has identified a large number of retailers who filed Form ST-1 returns for periods after January 1, 2021, with sales amounts reported only on lines 6a and 7a, the lines used to report tax on sales subject only to Illinois Use Tax. These retailers may not be properly assessing, collecting, remitting, and reporting Illinois taxes on some or all of their sales. Some of their sales may be subject to Retailers’ Occupation Tax at the origin rate or destination rate, depending on the specifics of each sale.