CT-1120 ES: Estimated Corporation Business Tax Payment Coupons (2025)
Connecticut · Connecticut DRS · Used for tax years 2025
Form CT-1120 ES provides payment coupons and calculations for four installments of estimated Connecticut Corporation Business Tax for 2025. Each coupon identifies the corporation or designated taxable member and reports the payment amount due. Filing and payment must be electroni
Who files this form
Every corporation or combined group carrying on business, or having the right to carry on business, in Connecticut must file if its estimated current-year tax liability on Schedule 1, Line 5, is more than $1,000.
For combined unitary filers, the designated taxable member should make all estimated tax payments using its Connecticut Tax Registration Number.
When it's due
For the 2025 income year, the installment due dates are:
- First installment, CT-1120 ESA: 15th day of the 3rd month of the income year.
- Second installment, CT-1120 ESB: 15th day of the 6th month of the income year.
- Third installment, CT-1120 ESC: 15th day of the 9th month of the income year.
- Fourth installment, CT-1120 ESD: 15th day of the 12th month of the income year.
If a due date falls on a Saturday, Sunday, or legal holiday, the return is considered timely if filed by the next business day.
What you'll need
Have the following information ready to complete the coupons and Schedule 1:
- Connecticut Tax Registration Number and Federal Employer ID Number (FEIN).
- Corporation or designated taxable member name, address, income-year ending date, and return type: Separate or Combined Unitary.
- Tax shown on the prior-year return, including surtax and before tax credits.
- Estimated current-year tax before credits and estimated Corporation Business Tax credits.
- Prior-year overpayment and any earlier estimated installments paid for the current year.
- Worksheet CT-1120AE, if using annualized income installments.
Attach an explanation if the closing month has changed. Paper coupons may be filed only if DRS has granted an electronic filing waiver.
How to file
Complete Schedule 1 for the installment to calculate the payment amount. Enter the amount from Line 9 on the coupon's payment amount due line.
File and pay electronically through myconneCT at portal.ct.gov/DRS-myconneCT.
Paper filing is allowed only with a DRS waiver. Form DRS-EWVR, Electronic Filing and Payment Waiver Request, is available at portal.ct.gov/DRS.
If DRS has granted a waiver from electronic filing and payment:
- Complete the coupons in blue or black ink only.
- Make the check payable to Commissioner of Revenue Services.
- Write “2025 Form CT-1120” and the corporation's Connecticut Tax Registration Number on the front of the check.
- Do not use staples.
Mail to:
Department of Revenue Services
State of Connecticut
PO Box 2974
Hartford, CT 06104-2974
Common mistakes
- Mailing paper coupons without a waiver: The return must be filed and paid electronically unless DRS grants a waiver.
- Using the wrong year's form: The form warns that submitting the correct year's form is required to prevent processing delays.
- Leaving identifying information off a check: Include “2025 Form CT-1120” and the corporation's Connecticut Tax Registration Number so the payment goes to the correct account.
- Using staples or the wrong ink for paper coupons: Do not use staples. Use blue or black ink only.
- Omitting an explanation when the closing month changes: The coupon requires an attached explanation.
Questions people ask
Can I mail my estimated tax payment coupon?
Only taxpayers who receive a DRS electronic filing waiver may file paper estimated payment coupons. Otherwise, file and pay electronically through myconneCT.
Who makes estimated payments for a combined unitary group?
The designated taxable member should make all estimated payments using its Connecticut Tax Registration Number. The prior-year tax used for Schedule 1, Line 1, is the total tax due from all taxable members of the combined group that filed with that designated taxable member in the prior year.
How do I account for payments already made?
Schedule 1, Line 8, includes the prior-year overpayment. For the second, third, and fourth installments, it also includes payments made with the earlier coupons. Line 9 subtracts Line 8 from Line 7 to calculate the payment due.
Can I use an annualized income installment?
If the corporation establishes that its annualized income installment is less than Schedule 1, Line 9, it must enter the amount from Worksheet CT-1120AE, Line 20, on Line 9. Use Column A for the first installment, B for the second, C for the third, and D for the fourth.