Illinois R&D Income Tax Credit

Illinois R&D Income Tax Credit

Funds Illinois innovators through income tax credits for innovation in startups and established companies.

Eligibility · United States · US-IL

The Illinois R&D Income Tax Credit is a statutory, self-claimed tax credit equal to 6.5% of qualifying Illinois research and development expenses in excess of the taxpayer's base-period average. Codified at 35 ILCS 5/201(k), the credit mirrors the structure of the federal research credit under IRC §41 — requiring that qualified activities meet the four-part test of qualified purpose, technological nature, elimination of uncertainty, and a process of experimentation — but is computed separately using only Illinois-apportioned QREs. The credit carries forward for five years and is claimed on Schedule 1299-D (for business filers) or Schedule 1299-C (for individual filers) attached to the annual Illinois income tax return. No pre-certification or application to the Illinois Department of Revenue (IDOR) is required; the taxpayer self-calculates and claims the credit at filing, with IDOR retaining audit authority.

The program is sector-agnostic: any corporation, partnership, S-corporation, LLC, or individual with qualifying Illinois research activity is eligible, spanning industries from manufacturing and software to life sciences and engineering. The current legislative sunset is 2027, making the credit a temporary but renewable incentive subject to periodic extension. Estimated annual credit values range from a few thousand dollars for small R&D operations to $2 million or more for mid-sized companies with substantial Illinois-based research payrolls, though there is no per-taxpayer statutory cap. Because IDOR is the sole administering body — unlike some Illinois credits where the Department of Commerce and Economic Opportunity (DCEO) issues certifications — the credit requires no separate agency interaction beyond the annual tax filing.

Companies conducting research and development in Illinois benefit most from this credit by maintaining contemporaneous QRE documentation aligned with federal IRC §41 standards, as IDOR audits typically follow IRS examination techniques. The 6.5% rate on incremental Illinois QREs, combined with the federal rate (up to 20% of incremental QREs under IRC §41), means that Illinois-based R&D operations can achieve a combined effective credit rate that materially reduces the after-tax cost of research investment.