Why Chicago is different
Chicago's cost-seg picture has two layers: a clean federal-acceleration story under OBBBA's restored 100% bonus depreciation, and a more complex Illinois state-side picture that's frequently misrepresented elsewhere. Illinois is not fully conforming on federal §168(k). The Illinois Income Tax Act (35 ILCS 5/203) requires addition modifications for federal bonus depreciation with subsequent subtraction modifications that recover the deduction across multiple Illinois tax years, your federal Year-1 cash captures cleanly, but the Illinois-side benefit is spread rather than fully accelerated. A Chicago investor taking $80,000 of accelerated reclassification at the 37% federal bracket captures $29,600 of Year-1 federal cash, with the Illinois-side $3,960 total benefit spread over multiple state tax years rather than concentrated in Year 1. The federal benefit is real; the Illinois timing math is more complex than a simple flat-rate calculation suggests.
The bigger practical constraint on Chicago cost-seg is the regulatory STR environment. Chicago's Shared Housing Ordinance restricts short-term rental operations to registered hosts with significant compliance requirements, limits on density, and restrictions on whole-unit non-primary-residence STR. Most cost-seg-relevant Chicago property operates as long-term rental, pre-war SFR fix-and-flip in Lincoln Park, Bucktown, and Wicker Park; two-flat and three-flat small-multifamily acquisitions in Logan Square, Avondale, and Pilsen; downtown-adjacent condo rental in South Loop and West Loop; and suburban Cook County SFR rental in Oak Park and Evanston (outside Chicago city jurisdiction).
The structural cost-seg case is unusually strong on Chicago two-flats and three-flats. The 1890s–1920s small-multifamily stock in Logan Square, Avondale, Pilsen, and Bridgeport typically features multiple FF&E packages per building (each unit has its own kitchen, bathrooms, appliances), shared-system depreciation considerations (boiler, electrical service, structural masonry), and substantial post-2000 renovation cost pools. Engine reclassification ratios on pre-war two-flat and three-flat acquisitions can run 24–32% when the property has well-documented post-2010 renovation, among the higher LTR ratios in our network, though individual results vary based on specific renovation history and property condition.
Illinois state tax position: Illinois generally follows federal MACRS rules but is NOT fully conforming on federal §168(k) bonus depreciation. The Illinois Income Tax Act requires addition modifications for federal bonus depreciation, with subsequent subtraction modifications that recover the deduction over multiple Illinois tax years rather than concentrating it in Year 1. For 2025+ acquisitions under OBBBA's 100% federal bonus, the federal §168(k) acceleration captures cleanly in Year 1, but the Illinois-side benefit is spread across multiple years rather than fully accelerated. Verify current-year Illinois treatment with your CPA; IL bonus depreciation conformity has been adjusted multiple times in recent years and continues to evolve through 2026 legislation.
Decoupling: Illinois has historically required IL Schedule M addition modifications for federal bonus depreciation, with corresponding subtraction modifications recovering the deduction over future Illinois tax years. Model federal and Illinois treatment separately, they do not match year-by-year even when the total deduction is equivalent over the property's holding period.
Verify with your CPA. State tax conformity rules for federal §168(k) bonus depreciation are adjusted frequently, multiple states have modified their treatment two or more times in the past decade. The general framing on this page reflects our understanding as of May 2026, but you should always verify current-year treatment with a qualified CPA or tax attorney before relying on specific dollar projections for your situation.
