Schedule CT-SI: Nonresident or Part-Year Resident Schedule of Income from Connecticut Sources (Revision 2025-12)
Connecticut · Connecticut DRS · Used for tax years 2025
Schedule CT-SI is Connecticut’s 2025 income schedule for nonresidents and part-year residents. It reports income from Connecticut sources and related adjustments to calculate the amount entered on Form CT-1040NR/PY.
Who files this form
Complete the 2025 Schedule CT-SI if you were a nonresident or part-year resident of Connecticut. Attach it to Form CT-1040NR/PY.
- Nonresidents: Enter income received from Connecticut sources.
- Part-year residents: Complete Schedule CT-1040AW, Part-Year Resident Income Allocation. Add Columns B and D for each line and enter the totals on Schedule CT-SI, Lines 1 through 30.
What you'll need
Have these forms and details available:
- Form CT-1040NR/PY, to which you must attach Schedule CT-SI.
- Schedule CT-1040AW, if you were a part-year resident.
- Your name and Social Security number, plus your spouse’s name and Social Security number if filing jointly.
- Amounts for the income and related adjustments reported on Schedule CT-SI.
- If you need the Employee Apportionment Worksheet, working days inside and outside Connecticut, nonworking days, and total income being apportioned. If using a basis other than working days, identify that basis.
How to file
Attach Schedule CT-SI to Form CT-1040NR/PY. Do not use staples, and complete the schedule in blue or black ink only.
Enter the amount from Schedule CT-SI, Line 30, on Form CT-1040NR/PY, Line 6.
Before completing the schedule, visit Connecticut DRS Individual Income Tax, as directed on the form.
Common mistakes
- Using the wrong year’s form: Each form is year specific. Use the 2025 edition for tax year 2025 to avoid processing delays.
- Stapling the schedule: The form says not to use staples.
- Using another ink color: Complete the schedule in blue or black ink only.
- Completing the apportionment worksheet unnecessarily: Do not complete Lines A through G if you know the exact amount of your Connecticut-sourced employment income. Complete them only when employment income was earned both inside and outside Connecticut and the exact Connecticut amount is unknown.
- Including unrelated adjustments: Part 2 allows adjustments directly related to the income reported above it.
Questions people ask
How do I calculate my Connecticut employment income if I worked inside and outside the state?
If the exact Connecticut income amount is unknown, complete Employee Apportionment Worksheet Lines A through G. Divide Line B by Line C and round the ratio to four decimal places. Multiply that ratio by Line F, the total income being apportioned. Enter the result on worksheet Line G and Schedule CT-SI, Line 1.
Can I use a basis other than working days for the worksheet?
The worksheet provides for working days or another basis. If you use another basis, identify it in the space provided.
How do I calculate income from Connecticut sources on Line 30?
Add Lines 1 through 14 to get gross income on Line 15. Add adjustments on Lines 16 through 28 to get Line 29. Subtract Line 29 from Line 15 and enter the result on Line 30.
Where do I enter the final amount on my return?
Enter Schedule CT-SI, Line 30, on Form CT-1040NR/PY, Line 6.