2 Guides across 1 job. Each Guide is authored by an accountant; the ones more colleagues stand behind rise to the top.
Illinois Individual Income Tax Return (Form IL-1040) for sole proprietors and single-member LLCs. Covers the flat 4.95% rate, Illinois base income computation from federal AGI, Schedule M addition and subtraction modifications, property tax credit (Schedule ICR), earned income credit, and the full return assembly. Primary source: 35 ILCS 5/.
Illinois Estimated Income Tax (Form IL-1040-ES) for self-employed individuals. Covers quarterly payment requirements, 4.95% flat rate computation, safe harbour rules, underpayment penalty calculation, and payment schedule. Primary source: 35 ILCS 5/803; 86 Ill. Admin. Code 100.8010.