Concord — A health insurance cooperative based in Maine has informed New Hampshire insurance regulators that next year it will stop providing coverage in the Granite State, where 11,600 people are currently covered by its group and individual policies.

Community Health Options, a Lewiston, Maine, organization that was formed with federal financial backing authorized by the Affordable Care Act, is one of five insurers that together currently cover more than 90,000 New Hampshire residents with individual policies sold through the federally operated marketplace, the online health insurance exchange where individuals shop for coverage.

Community Health Options and Harvard Pilgrim’s New Hampshire Network are the only two individual plans sold on the marketplace that include all 26 of the state’s hospitals in their provider networks, according to a summary compiled by the New Hampshire Insurance Department.

But Community Health Options, which began selling insurance in Maine in 2014 and expanded into New Hampshire last year, now covers fewer than 3,500 New Hampshire residents through individual marketplace policies. In December 2015, it stopped selling new policies and, with less than a 4 percent share of that market, it trailed the other four insurers competing for business in that venue.

Anthem Blue Cross Blue Shield of New Hampshire, with about 29,600 covered individuals and a 33 percent market share, is the largest marketplace provider, followed by three insurers, each with about 19,000 covered individuals.

One of Anthem’s competitors is Minuteman Health Inc., a Massachusetts-based co-op, which in July filed a lawsuit in U.S. District Court in Washington, D.C., alleging that it would need to increase marketplace rates because of a faulty methodology used by the U.S. Centers for Medicare and Medicaid Services. Minuteman initially sought 2017 rate increases for its New Hampshire marketplace policies ranging from 18 to 28 percent.

Minuteman’s lawsuit challenges a formula that the Centers for Medicare and Medicaid Services use to calculate assessments under a risk-adjustment program designed to offset higher costs taken on by marketplace insurers who cover less healthy individuals. The alleged faulty formula resulted in Minuteman being forced to pay its competitors more than $10 million, or more than two out of every five dollars collected in premiums in New Hampshire, the lawsuit said.

On Aug. 9, Community Health Options announced that it had filed its own lawsuit claiming that the U.S. Department of Health and Human Services had failed to pay it $23 million owed under another risk-adjustment program. Community Health Options, which posted a $31 million deficit in 2015, provides group or individual health insurance to more than 66,000 residents of Maine, according to the New Hampshire Insurance Department.

Community Health Options’s latest announcement did not include a deficit projection for the current year but said that by leaving the Granite State, where it had previously indicated it would seek approval for 2017 premium increases ranging from 32 percent 60 percent on its marketplace plans, it would “strengthen its capital position in its dominant market and rebuild its reserves to accommodate future growth.”

Community Health Options covered 1,400 New Hampshire residents who bought insurance policies to obtain coverage under the state’s Medicaid expansion program, known as New Hampshire Health Protection. That program provides premium assistance to low-income people for the purchase of certain marketplace policies. Those individuals will each receive a letter informing them that they must choose a new plan for 2017, the New Hampshire Insurance Department said.

Community Health Options urged all of its current New Hampshire customers “to enroll in a new plan as soon as possible, on or after” the beginning of the next open season on Nov. 1. The New Hampshire Insurance Department said it “advises residents to select a new plan by Dec. 15 in order to ensure a smooth transition.”

Community Health Options and New Hampshire regulators agreed on one thing: Current Community Health Options plans would continue to provide coverage until Dec. 31. Claims could be submitted up to 12 months after the termination of coverage, Community Health Options said.

Rick Jurgens can be reached at rjurgens@vnews.com or 603-727-3229.