Amends the Retailers' Occupation Tax Act. Provides that a retailer that makes retail sales of tangible personal property to Illinois customers from a location or locations outside of Illinois is engaged in the occupation of selling at retail in Illinois for the purposes of the Retailers' Occupation Tax Act under specified conditions. Provides that a retailer maintaining a place of business in this State that makes retail sales of tangible personal property to Illinois customers from a location or locations outside of Illinois is engaged in the business of selling at the Illinois location to which the tangible personal property is shipped or delivered or at which possession is taken by the purchaser. Effective January 1, 2025.