Illinois DOR Proposes Amending Income Tax Rules on Combined Reporting, Nexus Standards

The Illinois Department of Revenue (DOR) proposed amendments to income tax rules regarding combined reporting and nexus standards. The proposal includes measures to implement Public Act 104-0006, which requires unitary business groups to use the “Finnigan” method for apportioning sales within the group for tax years ending on or after Dec. 31, 2025, and to update provisions on combined returns, combined tax liability, and nexus standards. The public comment period ends Feb. 16. [Ill. Dep’t of Revenue, Proposed Regs. Sections 100.3200 et al., 01/02/26 Ill. Reg.]