Check our 2026 Tax Deadlines For C-Corp Startups or Click for your customized tax compliance calendar by startup hub
Startup companies based in Chicago have several important tax deadlines in 2026, including the April 15th federal and Illinois tax return filings (which can be extended until October 15th). Additionally, Illinois and the federal government have various tax filings due on the dates listed below.
Quarterly Payroll Withholding Report due for Illinois – Quarter 4.
Claim Research & Development Tax Credits on Form 941, and file annual Federal Unemployment Tax Act (FUTA) return on Form 940. Use our handy calculator to estimate your possible research and development tax credit.
Chicago startups should send 1099s to contractors. Send W2s to employees and e-file 1099-MISC for non-employee compensation with the IRS. Or file Form 8809 for a 30-day extension to file W2s and 1099-MISC for non-employee compensation.
Delaware Annual Franchise Report filing deadline. Your Chicago startup will pay a minimum of $400, which increases if you have significant funding.
For Chicago startups, IRS ACA Compliance 1094-B, 1095-B, 1094-C, and 1095-C filings are due (if paper-filing, due April 1 if eFiling). File Form 8809 for a 30-day extension.
Send 1095-B and 1095-C forms to employees.
IRS 30-day automatic extension: provide Form 1095-B and Form 1095C to employees.
IRS ACA Compliance 1094-B, 1095-B, 1094-C, and 1095-C filings are due (e-file).
Due date for Illinois Corporate Income Tax Return (can be extended to September 15).
C Corp Form 1120 Tax Return due. The Federal Form 1120 is the U.S. Corporation Income Tax Return, which the IRS has companies use to report their income, losses, credits, etc., and to figure the income tax liability of the corporation. Can extend the deadline to Oct. 15. All Chicago startups are required to file this Federal form by this deadline unless they file an extension.
Federal Quarterly Estimated Tax 1st installment (first quarter 2026).
File the R&D Tax Credit Form 6765 with your tax return. Can extend to October 15. We strongly recommend working with a qualified CPA to prepare this form in conjunction with your Form 1120 if your company is going to be acquired by a major technology company, that company’s CFO will use a strong tax team to do due diligence on this.
Due date for Chicago startup employees to make contributions to Individual Retirement Accounts (IRAs) for 2025 (Employee Benefits).
Quarterly Payroll Withholding Report due for Illinois – Quarter 1.
Chicago startups can claim Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax. Pay 40% of estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 2nd installment (second quarter 2026).
Quarterly Payroll Withholding Report due for Illinois – Quarter 2.
Claim Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax. Pay 20% of your estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 3rd installment (third quarter 2026).
C Corp Form 1120 Tax Return final due date for Chicago startups if extension was filed.
Quarterly Payroll Withholding Report due for Illinois – Quarter 3.
Claim your Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax, Pay 20% of estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 4th installment (fourth quarter 2026).
Click The Links To Learn More About These Filings And 2026 Chicago Startup Tax Deadlines
Federal Quarterly Estimated Tax 4th installment (fourth quarter 2025).
Quarterly Payroll Withholding Report due for Illinois – Quarter 4.
Claim Research & Development Tax Credits on Form 941, and file annual Federal Unemployment Tax Act (FUTA) return on Form 940. Use our handy calculator to estimate your possible research and development tax credit.
Chicago startups should send 1099s to contractors. Send W2s to employees and e-file 1099-MISC for non-employee compensation with the IRS. Or file Form 8809 for a 30-day extension to file W2s and 1099-MISC for non-employee compensation.
Delaware Annual Franchise Report filing deadline. Your Chicago startup will pay a minimum of $400, which increases if you have significant funding.
For Chicago startups, IRS ACA Compliance 1094-B, 1095-B, 1094-C, and 1095-C filings are due (if paper-filing, due April 1 if eFiling). File Form 8809 for a 30-day extension.
Send 1095-B and 1095-C forms to employees.
IRS 30-day automatic extension: provide Form 1095-B and Form 1095C to employees.
IRS ACA Compliance 1094-B, 1095-B, 1094-C, and 1095-C filings are due (e-file).
Due date for Illinois Corporate Income Tax Return (can be extended to September 15).
C Corp Form 1120 Tax Return due. The Federal Form 1120 is the U.S. Corporation Income Tax Return, which the IRS has companies use to report their income, losses, credits, etc., and to figure the income tax liability of the corporation. Can extend the deadline to Oct. 15. All Chicago startups are required to file this Federal form by this deadline unless they file an extension.
Federal Quarterly Estimated Tax 1st installment (first quarter 2026).
File the R&D Tax Credit Form 6765 with your tax return. Can extend to October 15. We strongly recommend working with a qualified CPA to prepare this form in conjunction with your Form 1120 if your company is going to be acquired by a major technology company, that company’s CFO will use a strong tax team to do due diligence on this.
Due date for Chicago startup employees to make contributions to Individual Retirement Accounts (IRAs) for 2025 (Employee Benefits).
Quarterly Payroll Withholding Report due for Illinois – Quarter 1.
Chicago startups can claim Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax. Pay 40% of estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 2nd installment (second quarter 2026).
Quarterly Payroll Withholding Report due for Illinois – Quarter 2.
Claim Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax. Pay 20% of your estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 3rd installment (third quarter 2026).
C Corp Form 1120 Tax Return final due date for Chicago startups if extension was filed.
Quarterly Payroll Withholding Report due for Illinois – Quarter 3.
Claim your Research & Development Tax Credits on Form 941.
Extended due date for Illinois Corporate Income Tax Return.
Delaware Quarterly Estimated Franchise Tax, Pay 20% of estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 4th installment (fourth quarter 2026).
Note: The federal tax deadline in 2026 falls on April 15. The federal extension deadline for 2026 is October 15. Most states usually follow the same calendar for state income tax returns
If your Delaware C-Corp Chicago funded startup needs tax help contact us today!
CHICAGO, STARTUPS AND TAXES
Chicago stands out in 2026 as a top innovation hub, ranking 6th in the U.S. and 19th globally for startup ecosystems, with over 2,000 startups spanning fintech, healthtech, foodtech, logistics, ecommerce, and B2B SaaS. While funding volume fluctuated in recent years, the city saw strong momentum in early-stage and scale-up financing – over $3.6 billion in startup capital was deployed in 2025, supported by a deeply rooted investor base and accelerator community. Chicago’s customer base is robust, with more than 30 Fortune 500 headquarters and a diversity of industries – no sector drives more than 14% of the regional economy, making it attractive for founders in any vertical.
Chicago’s business culture is especially collaborative, offering access to a wide pool of talent from major universities and corporate partners. Notable programs and events such as Techstars Chicago and the annual Venture Capital World Summit help founders connect with capital, mentorship, and growth resources. Investors, incubators, and service providers are plentiful – more than 350 startup resources are available locally.
Key taxing authorities for Chicago-based businesses in 2026 are:
Chicago’s diverse business ecosystem, deep talent pool, and active VC networks continue to position it as a vibrant city for startup founders seeking growth and connections in 2026.
In 2026, Chicago-based companies have several important tax deadlines, including the April 15th federal and Illinois tax return filings (which can be extended until October 15th). Additionally, Illinois and the federal government have various tax filings due on the dates listed above.
2025 startup tax deadlines are supplied for reference purposes only, and should not be used when making decisions in 2026 or beyond. Always consult your tax professional, and see our disclaimer below.
Click The Links To Learn More About These Filings And 2025 Chicago Startup Tax Deadlines
Quarterly Payroll Withholding Report due for Illinois – Quarter 4.
Claim Research & Development Tax Credits on Form 941, and file annual Federal Unemployment Tax Act (FUTA) return on Form 940. Use our handy calculator to estimate your possible research and development tax credit.
Delaware Annual Franchise Report filing deadline. Your Chicago startup will pay a minimum of $400, which increases if you have significant funding.
IRS 30-day automatic extension: provide Form 1095-B and Form 1095C to employees.
Due date for Illinois Corporate Income Tax Return (can be extended to September 15).
C Corp Form 1120 Tax Return due. The Federal Form 1120 is the U.S. Corporation Income Tax Return, which the IRS has companies use to report their income, losses, credits, etc., and to figure the income tax liability of the corporation. Can extend the deadline to Oct. 15. All Chicago startups are required to file this Federal form by this deadline unless they file an extension.
Federal Quarterly Estimated Tax 1st installment (first quarter 2024).
File the R&D Tax Credit Form 6765 with your tax return. Can extend to October 15. We strongly recommend working with a qualified CPA to prepare this form in conjunction with your Form 1120 if you are a high-growth startup – if your company is going to be acquired by a major technology company, that company’s CFO will use a strong tax team to do due diligence on this.
Due date for Chicago startup employees to make contributions to Individual Retirement Accounts (IRAs) for 2023 (Employee Benefits).
Quarterly Payroll Withholding Report due for Illinois – Quarter 1.
Chicago startups can claim Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax. Pay 40% of estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 2nd installment (second quarter 2024).
Quarterly Payroll Withholding Report due for Illinois – Quarter 2.
Claim Research & Development Tax Credits on Form 941 .
Delaware Quarterly Estimated Franchise Tax. Pay 20% of your estimated annual amount (if annual amount expected to exceed $5,000).
Extended due date for Illinois Corporate Income Tax Return.
Federal Quarterly Estimated Tax 3rd installment (third quarter 2024).
C Corp Form 1120 Tax Return final due date for Chicago startups if extension was filed.
Quarterly Payroll Withholding Report due for Illinois – Quarter 3.
Claim your Research & Development Tax Credits on Form 941.
Delaware Quarterly Estimated Franchise Tax, Pay 20% of estimated annual amount (if annual amount expected to exceed $5,000).
Federal Quarterly Estimated Tax 4th installment (fourth quarter 2024).
View tax compliance dates for Austin, Boston, New York City, Palo Alto, San Francisco, Santa Monica, Seattle, Washington DC, Atlanta, Salt Lake City, Mountain View, Chicago, Dallas, Miami, and San Jose
How Much Does a Startup Tax Return Cost? Try Kruze Consulting's Tax Preparation Pricing Tool.
How much can your startup save in payroll taxes? Estimate your R&D tax credit using our free calculator.
Every startup is different and so are its tax compliance needs. This is only a guideline. Please consult your tax professional. IRS Circular 230 Disclaimer: To ensure compliance with IRS Circular 230, any U.S. federal tax advice provided in this communication is not intended or written to be used, and it cannot be used by the recipient or any other taxpayer for the purpose of avoiding tax penalties that may be imposed on the recipient or any other taxpayer. Copyright © Kruze Consulting
Check our 2026 Tax Deadlines For C-Corp Startups or Click for your customized tax compliance calendar by startup hub
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We build financial models that have been used to pitch (and secure millions in funding) from premier VC firms and top angel investors. We also provide 409A valuations, KPI dashboards, cap table management, venture debt consulting, budgeting, and much more.
Founder & CEO, Vanessa Kruze, is a CPA, Deloitte Tax alumni, and former Controller of a 120+ FTE startup. Our Staff Accountants and Controllers come from the Big 4 and venture backed startups.
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