Connecticut State AMT 2026 Add-On Calculator
Connecticut state AMT is a 7% tax on the federal tentative minimum tax base, with a $24,000 exemption and high-earner recapture. Computed on Form CT-6251 attached to CT-1040, it captures Connecticut-source preference items including ISO bargain element and depreciation.
| Federal AMTI | — |
| + CT add-backs | — |
| − CT subtractions | — |
| = Connecticut AMTI | — |
| CT AMT exemption | — |
| CT AMTI after exemption | — |
| Tentative CT AMT @ 7% | — |
| Less CT regular tax | — |
| + High-earner recapture (CT-1040 §) | — |
| Connecticut AMT owed (Form CT-6251) | — |
Connecticut state AMT is a 7% add-on tax computed on Form CT-6251 when the tentative state minimum tax exceeds Connecticut regular income tax. It uses a flat $24,000 exemption (across filing statuses) and adds back Connecticut-specific preferences such as non-Connecticut municipal bond interest. High earners may also face the separate Connecticut "tax recapture" that effectively flattens the bracket benefit.
How Connecticut State AMT Works
Connecticut imposes a parallel AMT under Conn. Gen. Stat. §12-700a. The base is federal AMTI adjusted for Connecticut differences — most commonly adding back interest from out-of-state municipal bonds and subtracting US federal bond interest. After the $24,000 exemption, 7% is applied. If tentative CT AMT exceeds CT regular income tax (computed on CT-1040), the difference is owed as state AMT and entered on CT-1040 line 9.
High-Earner Recapture and Effective Rate
Connecticut also imposes a "tax recapture" (Conn. Gen. Stat. §12-700) separate from AMT that phases out the benefit of lower brackets for filers above $200,000 single / $400,000 joint. The recapture can add several thousand dollars on top of CT AMT. The combined effect is that Connecticut high earners face a 6.99% top rate plus AMT exposure plus recapture — strict planning around ISO exercises and depreciation timing becomes essential.
Filing Requirements and Planning
Attach Form CT-6251 to CT-1040 whenever you owe federal AMT or have CT-specific preferences exceeding the exemption. (1) Time ISO exercises — bargain element on incentive stock options is a federal AMT preference and flows directly into CT AMTI. (2) Watch out-of-state muni interest — CT does not exempt it the way some states do; it adds back for both regular and AMT computation. (3) Track AMT credit carryforward on Form CT-8801, recoverable in years when CT regular tax exceeds tentative AMT. (4) Coordinate residency — partial-year residents apportion AMT and recapture by Connecticut-source income.
Last updated May 2026. Sources: Connecticut Department of Revenue Services Form CT-6251 Instructions, Conn. Gen. Stat. §12-700a.