CT-1120CU-MTB: Tax on Combined Group Minimum Tax Base (2025)
Connecticut · Connecticut DRS · Used for tax years 2025
Form CT-1120CU-MTB calculates the Connecticut tax on a combined group’s minimum tax base, also called its capital base. It reports members’ beginning- and end-of-year capital amounts, group adjustments, apportionment fractions, and the resulting tax.
Who files this form
Combined groups use Form CT-1120CU-MTB to calculate the tax on their combined minimum tax base, also called the capital base. Complete it and attach it to Form CT-1120CU.
Combined groups are subject to tax on the greater of their net income base or minimum tax base. The form calls for a column for each taxable and nontaxable member, with special rules for financial service companies, REITs and RICs.
What you'll need
- Federal Form 1120, Schedule L: Beginning- and end-of-year amounts from Lines 22a, 22b, 23, 24 and 25.
- Supporting schedules: Attach schedules for surplus reserves and holdings of stock of private corporations.
- Intercompany information: Amounts needed for adjustments and eliminations for intercorporate stock holdings and other transactions among group members.
- Form CT-1120CU-MI: Each member’s number and corporation name.
- Form CT-1120A-CU, Schedule S, or the appropriate apportionment form: Each taxable member’s minimum tax base apportionment fraction.
- Form CT-1120CU: Attach the completed CT-1120CU-MTB to this return.
Also have the designated taxable member’s Connecticut Tax Registration Number available.
How to file
Complete Form CT-1120CU-MTB and attach it to Form CT-1120CU. Enter the tax from Line 14 on Form CT-1120CU, Part I, Line 2.
Complete a column for each taxable and nontaxable member, following the special rules for financial service companies, REITs and RICs. If the group has more than six members, attach additional copies of Page 2 using the same format.
The supplied text does not give a mailing address or e-filing directions.
Common mistakes
- Reporting deficits as positive amounts: Any deficit included on Lines 1 or 4 must be reported as a negative number.
- Deducting stock holdings within the group: No deduction is allowed on Lines 2 or 5 for intercorporate stock holdings among combined group members.
- Using an apportionment fraction for a nontaxable member: Nontaxable members must enter zero on Line 8, subject to the special blank-line rules for financial service companies, REITs and RICs.
- Prorating the $250 minimum tax: Do not prorate any member’s $250 minimum tax when applying the group’s $1,000,000 limit.
- Completing unnecessary proration lines: If Line 11 is $1,000,000 or less, leave Lines 12 and 13 blank and go to Line 14.
- Missing the transfer to the main return: Also enter Line 14 on Form CT-1120CU, Part I, Line 2.
Questions people ask
How is the combined group’s average minimum tax base calculated?
Add the Combined Group Total amounts on Lines 3 and 6, then divide by two. Enter the result on Line 7.
What tax rate and limits apply?
Each taxable member’s apportioned minimum tax base is multiplied by 0.21% (.0021). The tax generally cannot be less than $250 for a taxable member, with special rules for REITs and RICs. The group’s aggregate minimum tax on capital cannot exceed $1,000,000 before the surtax. Do not prorate a member’s $250 minimum tax.
What should financial service companies, REITs and RICs enter?
Financial service companies leave Lines 1 through 9 blank. On Line 10, taxable financial service company members enter $250, and nontaxable financial service company members enter $0. REITs and RICs leave all lines in Parts A and B blank.
How does Public Law 86-272 affect the calculation?
If the only group member subject to the Corporation Business Tax is immune from Connecticut net income taxation under Public Law 86-272, the group calculates tax only on the minimum tax base. If other non-immune members are subject to the tax, the group calculates tax on both bases. It treats the immune member as nontaxable for the net income base and taxable for the minimum tax base.