More than 71,000 low- and middle-income Hawaii residents could be eligible for tax credits to help pay for health insurance when the first major piece of the federal Affordable Care Act takes effect in January, a study released Wednesday shows.

The report by Families USA, a national consumer health advocacy group based in Washington, D.C., said most people eligible for tax credits will be in working families, with incomes between two and four times the federal poverty level, or between $54,180 and $108,360 for a family of four based on 2013 poverty guidelines.

Eligible residents would be those without employer- or government-provided health insurance. Residents may also be eligible if they have health insurance but it costs more than 9.5 percent of their income.

The federal subsidies will be determined on a sliding scale based on income, providing the largest tax credits to residents with the lowest earnings.

Once the dollar amount of the subsidy is calculated, consumers can use the subsidy to purchase any health insurance plan available on a new state health insurance exchange. The tax credits will go directly to the health plan chosen, offsetting the total cost of the plan’s premiums for consumers.

The tax credits will significantly change the landscape for those who are currently uninsured and cannot afford the growing costs of health care, said Sheila Beckham, chief executive officer of Waikiki Health Center, a federally qualified community health center.

“Specifically, families and individuals who are within the gap group will benefit from these tax incentives,” she said. “This will mean increased access to care for many where this was simply out of reach before.”

The tax credits will not be available for full-time workers in Hawaii covered by employer health plans under the state’s Prepaid Health Care Act. It’s unclear whether the family of an insured worker would be eligible for the tax credits.

Separately, state Insurance Commissioner Gordon Ito said an estimated 21,000 small businesses in Hawaii may qualify for federal tax credits to help offset the cost of employee health insurance, with 4,900 eligible for a maximum tax credit of 35 percent this year and 50 percent next year for purchasing employee health insurance retroactive to 2010.

However, many small employers aren’t taking advantage of the program, he said.

“Either they don’t know about it or think that it might be too hard (to apply for the credit),” Ito said.

“They might think it’s too much time. We’re trying to encourage people to try and get the credit. We heard it’s kind of onerous to fill out the form, but 35 percent credit, that’s a lot.”

The study, based on data from the U.S. Census Bureau, also highlights eligible employees by county:

>> City and County of Honolulu: 42,350 residents will be eligible for the premium tax credit, and about 55 percent of those residents will be families with incomes between 200 percent and 400 percent of the federal poverty level.

>> Hawaii County: 13,720 people will be eligible, and about 55 percent of those residents will be families with incomes between 200 percent and 400 percent of the federal poverty level.

>> Kauai and Maui counties: 15,270 residents will be eligible for the premium tax credit, and about 59 percent of those residents will be families with incomes between 200 percent and 400 percent of the federal poverty level.