Short answer
Not right now, as far as public records show. Hawaiʻi had a cesspool upgrade, conversion or connection income tax credit, but it expired on December 31, 2020. A 2026 bill would bring it back, but it has not become law.
The old credit (2016 to 2020)
Act 120 (2015) created a credit of up to $10,000 for qualified expenses to upgrade or convert a qualified cesspool to a septic system or aerobic treatment unit, or connect it to sewer. It covered tax years 2016 through 2020 and had a $5 million yearly cap for all taxpayers. Only certain cesspools qualified, such as those near the shoreline, streams, wetlands or drinking water sources. Unused credits from those years can still be carried forward on Form N-323.
The 2026 bill (HB 2079)
HB 2079 would reestablish the credit for tax years beginning after December 31, 2026. Its measure page shows it passed second reading in the House in February 2026 and was referred to the Finance committee, with no later action listed. Treat it as a proposal, not a benefit you can count on.
What is available
The state's new Cesspool Conversion Revolving Loan Fund (Act 204 of 2026, from HB 1618) is meant to offer low-interest or forgivable loans through HGIA. See financing. Talk to a tax professional about your own situation.
Sources: Act 120 (2015); Form N-323 instructions; HB 2079 (2026); HB 1618 (2026)