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Complete 2025 Illinois Tax Calendar with all important state and federal tax filing deadlines at a glance.
| January | |
| 15 | 4th quarter estimate due |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended October 31 |
| 21 | Form ST-1 due (sales tax) |
| 31 | Form UI-3/40 due (payroll) |
| 31 | 1099s due to recipients |
| 31 | Form 940 due (payroll) |
| 31 | Forms 941 and IL-941 due (payroll) |
| 31 | W-2 due to recipients |
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| February | |
| 18 | Federal and State payroll tax deposits due for monthly depositors |
| 18 | C and S Corporations due for year ended November 30 |
| 20 | Form ST-1 due (sales tax) |
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| March | |
| 17 | Federal and State payroll tax deposits due for monthly depositors |
| 17 | SEP IRA Contribution due |
| 17 | S Corporations due for year ended December 31 |
| 20 | Form ST-1 due (sales tax) |
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| April | |
| 15 | TAX DAY |
| 15 | IRA contributions due (for prior year) |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended January 31 |
| 15 | 1st quarter estimate due |
| 15 | Partnerships and individual returns due |
| 15 | C Corporations due for year ended December 31 |
| 21 | Form ST-1 due (sales tax) |
| 30 | Form UI-3/40 due (payroll) |
| 30 | Form 941 and IL-941 due (payroll) |
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| May | |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended February 28 |
| 20 | Form ST-1 due (sales tax) |
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| June | |
| 16 | Federal and State payroll tax deposits due for monthly depositors |
| 16 | C and S Corporations due for year ended March 31 |
| 16 | 2nd quarter estimate due |
| 20 | Form ST-1 due (sales tax) |
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| July | |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended April 30 |
| 21 | Form ST-1 due (sales tax) |
| 31 | Form UI-3/40 due (payroll) |
| 31 | Forms 941 and IL-941 due (payroll) |
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| August | |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended May 31 |
| 20 | Form ST-1 due (sales tax) |
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| September | |
| 16 | Federal and State payroll tax deposits due for monthly depositors |
| 16 | C and S Corporations due for year ended June 30 |
| 16 | 3rd quarter estimate due |
| 16 | SEP IRA contribution due (if tax return extended) |
| 16 | Extended due date for C and S corporations |
| 22 | Form ST-1 due (sales tax) |
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| October | |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended July 31 |
| 15 | Extended due date for partnerships and individuals |
| 20 | Form ST-1 due (sales tax) |
| 31 | Form UI-3/40 due (payroll) |
| 31 | Forms 941 and IL-941 due (payroll) |
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| November | |
| 17 | Federal and State payroll tax deposits due for monthly depositors |
| 17 | C and S Corporations due for year ended August 30 |
| 20 | Form ST-1 due (sales tax) |
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| December | |
| 15 | Federal and State payroll tax deposits due for monthly depositors |
| 15 | C and S Corporations due for year ended September 30 |
| 22 | Form ST-1 due (sales tax) |
| 31 | Required Minimum Distribution (RMD) |