Helpful Information
Federal Tax Deadlines
April 15, 2025
Individual Tax Returns / Extensions — File Form 1040 (including Forms 1040A, 1040EZ) and pay any remaining tax due. You may request a 6-month extension using Form 4868 (new filing deadline: October 15, 2025). Chicagoland CPAs+1ICPA+1
1st Quarter Estimated Taxes — Deadline for individuals making estimated payments. 420 CPAIllinois Department of Revenue
C Corporation Returns — File Form 1120 and pay tax owed; automatic 6-month extension available until October 15, 2025. SVA Certified Public Accountants+12420 CPA+12Chicagoland CPAs+12
March 17, 2025
S Corporation & Partnership Returns Due — File Forms 1120S or 1065. Extensions can push deadlines to September 15, 2025. 420 CPA+2Instead+2
June 15, September 15, January 15 (2026)
Quarterly Estimated Individual Taxes — Second, third, and fourth estimated tax payments due on these dates, respectively. Illinois Department of Revenue+1
Helpful Information
Illinois State Tax Deadlines (2025)
April 15, 2026
Individual and C Corporation Returns — File Illinois Form IL-1040 and IL-1120 by this date; filing extensions granted automatically but payments remain due by April 15. Illinois Department of Revenue+7Corvee+7Instead+7
March 16, 2026
S Corporation Returns — Filing deadline for Illinois Form IL-1120S; extension to November 16, 2026. Corvee+1
April 15, 2026
Partnership Returns — Illinois Form IL-1065 due; extension through October 15, 2026. TurboTax+3Corvee+3Instead+3
Estimated Payments for Individuals (2025)
Due: April 15, June 16, September 15 (2025), and January 15 (2026) — ensure accurate payment to avoid Illinois penalties. Chicagoland CPAs+10Instead+10Illinois Department of Revenue+10
Illinois Withholding Tax
(Form IL-941)
Illinois employers must reconcile withholding with Form IL-941 quarterly, with deadlines generally as follows
Q1 (Jan–Mar): April 30, 2025
Q2 (Apr–Jun): July 31, 2025
Q3 (Jul–Sep): October 31, 2025
Q4 (Oct–Dec): February 2, 2026 (adjustment for holidays/weekends) SVA Certified Public Accountants+14Illinois Department of Revenue+14Claremont Management+14
Additional Important Dates
eCommerce companies work with us because we understand the unique mix of online platforms, sales taxes, and fulfillment costs that define their business model. From reconciling marketplace sales to managing multi-state compliance, our CPAs provide solutions that improve efficiency and strengthen profitability.
General Federal Payroll Filing (Form 941, FUTA, Tips Reporting)
Follow IRS’s quarterly schedule (similar to your previous page layout).
Tax Amnesty Program (Illinois) — October 1 – November 15, 2025
unpaid taxes from July 2018 through July 2024 (franchise and certain sales taxes). SVA Certified Public Accountants
Professional Bookkeeping for eCommerce Companies
Our bookkeeping services ensure accurate tracking of sales across Shopify, Amazon, eBay, and other platforms. By reconciling accounts and organizing records, we give eCommerce companies reliable financial visibility and confidence during tax season or fundraising.
Ready to work with a CPA firm that understands online retail? Contact us today for expert tax, payroll, and bookkeeping services designed for eCommerce businesses in Chicago and Illinois.
Helpful Information
Quick Reference Table
Deadline | Filing Requirement |
April 15, 2025 | Individual returns, 1st quarter estimates, C Corps |
March 17, 2025 | S Corp & Partnership returns |
June 16, 2025 | 2nd quarter estimated taxes |
September 15, 2025 | 3rd quarter estimated taxes |
January 15, 2026 | 4th quarter estimated tax due |
April 15, 2026 | Illinois individual & C corp taxes due |
March 16, 2026 | IL S Corp returns due |
IL Quarterly Filings | IL-941 due in April, July, October, February |
Oct 1 – Nov 15, 2025 | IL Tax Amnesty period |
