CT-1120A-CU: Apportionment Computation for Combined Unitary Filers (Revision 2025-12)
Connecticut · Connecticut DRS · Used for tax years 2025
Form CT-1120A-CU calculates net income and minimum tax base apportionment for Connecticut combined unitary filers. It reports members’ Connecticut and everywhere receipts, intangible assets, and tangible property to determine each taxable member’s apportionment.
Who files this form
Combined unitary filers use Form CT-1120A-CU to calculate each taxable member’s apportionment fraction for the net income and minimum tax bases. Complete it and attach it to Form CT-1120CU.
- A group may apportion its net income if any member does business outside Connecticut or is a financial services company as defined in the instructions.
- A group may apportion its minimum tax base if any member does business outside Connecticut.
What you'll need
Have these forms and records available:
- The designated taxable member’s Connecticut tax registration number.
- Form CT-1120CU-MI, which provides each member’s number, and each corporation’s name.
- Connecticut and everywhere receipts for each taxable and nontaxable member.
- Average monthly net book values of intangible assets and tangible property, with Connecticut and everywhere amounts identified.
- Information about transactions between group members and receipts subject to special apportionment rules.
- Form CT-1120CU, plus Form CT-1120CU-NI and Form CT-1120CU-MTB, where the calculated fractions are also entered.
How to file
Complete Form CT-1120A-CU and attach it to Form CT-1120CU.
- Use Schedule Q to calculate net income apportionment. Also enter each taxable member’s fraction on Form CT-1120CU-NI, Part III, Line 4.
- Use Schedule S to calculate minimum tax base apportionment. Also enter each taxable member’s fraction on Form CT-1120CU-MTB, Line 8.
The supplied text does not give a mailing address or e-file directions.
Common mistakes
- Do not include receipts from transactions between combined group members in net income apportionment.
- Exclude receipts from activities subject to special apportionment from Schedule Q.
- Exclude receipts from sales or other dispositions of property not held primarily for sale to customers in the ordinary course of business.
- On Schedule S, exclude stock holdings in private corporations and eliminate intercorporate stockholdings. Also eliminate assets and liabilities attributable to transactions between unitary group members.
- Financial service companies, real estate investment trusts, and regulated investment companies should enter zero for Connecticut and everywhere asset values.
- Prorate a part-year member’s average monthly net book value of assets to reflect the portion of the group’s income year that it was a member.
Questions people ask
How are nontaxable members’ Connecticut receipts handled?
They are assigned to taxable members in proportion to each taxable member’s share of all taxable members’ Connecticut receipts.
Whose everywhere receipts go into Schedule Q?
Include everywhere receipts for both taxable and nontaxable members, subject to the exclusions in the instructions. The group total is the denominator used to calculate each taxable member’s fraction.
How many decimal places should I use?
Carry the calculations on Schedule Q, Lines 3 and 10, and Schedule S, Line 8, to six decimal places.
Is the minimum tax base also called the capital base?
Yes. The instructions say the minimum tax base is sometimes called the capital base. Combined groups are subject to tax on the greater of their net income base or minimum tax base.