# Connecticut — State conformity to federal Section 179 and bonus depreciation rules

For Connecticut, section 179 conformity is conforms with state cap; state section 179 cap is 80% of IRC § 179 deduction is disallowed; 25% of disallowed portion allowed in each of the four succeeding income years; state section 179 phase-out is state rules apply; bonus depreciation conformity is decouples — requires add-back; add-back rule is any additional allowance for bonus depreciation under IRC § 168(k) must be added back; 25% of the disallowed deduction may be deducted for each of the four succeeding tax years, recorded from its source on 2026-08-15.

- **State:** Connecticut _(verified: appears in the quote below)_
- **Section 179 conformity:** conforms with state cap
- **State Section 179 cap:** 80% of IRC § 179 deduction is disallowed; 25% of disallowed portion allowed in each of the four succeeding income years
- **State Section 179 phase-out:** state rules apply
- **Bonus depreciation conformity:** decouples — requires add-back
- **Add-back rule:** any additional allowance for bonus depreciation under IRC § 168(k) must be added back; 25% of the disallowed deduction may be deducted for each of the four succeeding tax years
- **Has income tax:** yes _(verified: appears in the quote below)_

## What the source says

> Yes Colorado conforms to the Tax Cuts and Jobs Act provision that increases the maximum amount a taxpayer may expense under IRC Section 179 to $1 million, increases the phase-out threshold amount to $2.5 million, and provides for indexing for inflation State Follows Bonus Depreciation-TCJA of 2017 : No Connecticut

## Sources disagree

More than one authority states this, and they do not state the same
thing. Both are reproduced with the source each came from.

### State Section 179 cap

accountants.intuit.com says state section 179 cap is **80% of IRC § 179 deduction is disallowed; 25% of disallowed portion allowed in each of the four succeeding income years**, as of 2026-08-15.

> Yes Colorado conforms to the Tax Cuts and Jobs Act provision that increases the maximum amount a taxpayer may expense under IRC Section 179 to $1 million, increases the phase-out threshold amount to $2.5 million, and provides for indexing for inflation State Follows Bonus Depreciation-TCJA of 2017 : No Connecticut

Source: https://accountants.intuit.com/support/en-us/help-article/asset-depreciation/state-conformity-special-depreciation-allowance/L27kRyetJ_US_en_US

crosslinktax.com says state section 179 cap is **spread over 4 years**, as of 2026-08-15.

> Connecticut | Over 4 years | Over 4 years |

Source: https://www.crosslinktax.com/customer-resources/tax-resource-center/tax-updates/state-compliance-with-federal-bonus-depreciation-and-section-179-expensing-2025/


### Add-back rule

accountants.intuit.com says add-back rule is **any additional allowance for bonus depreciation under IRC § 168(k) must be added back; 25% of the disallowed deduction may be deducted for each of the four succeeding tax years**, as of 2026-08-15.

> Yes Colorado conforms to the Tax Cuts and Jobs Act provision that increases the maximum amount a taxpayer may expense under IRC Section 179 to $1 million, increases the phase-out threshold amount to $2.5 million, and provides for indexing for inflation State Follows Bonus Depreciation-TCJA of 2017 : No Connecticut

Source: https://accountants.intuit.com/support/en-us/help-article/asset-depreciation/state-conformity-special-depreciation-allowance/L27kRyetJ_US_en_US

crosslinktax.com says add-back rule is **bonus depreciation spread over 4 years**, as of 2026-08-15.

> Connecticut | Over 4 years | Over 4 years |

Source: https://www.crosslinktax.com/customer-resources/tax-resource-center/tax-updates/state-compliance-with-federal-bonus-depreciation-and-section-179-expensing-2025/


## Source

- https://accountants.intuit.com/support/en-us/help-article/asset-depreciation/state-conformity-special-depreciation-allowance/L27kRyetJ_US_en_US
- https://www.crosslinktax.com/customer-resources/tax-resource-center/tax-updates/state-compliance-with-federal-bonus-depreciation-and-section-179-expensing-2025/

Last verified: 2026-08-15. Review by: 2027-08-15.
Part of [State conformity to federal Section 179 and bonus depreciation rules](https://referencesource.org/state-section-179-bonus-depreciation-conformity/).