Health Net Inc. has agreed to pay a $13 million fine and $28 million in other penalties and costs for a decade of underpaying out-of-network claims from its New Jersey members.

The Woodland Hills health insurer waived its right to a hearing on the charge, the New Jersey Department of Banking and Insurance said Tuesday in a statement. The fine, which came after a 21-month investigation, was a record for the state.

Health Net of New Jersey paid $26 million in restitution and interest to compensate 88,000 subscribers for “dramatically underpaid claims,” according to the statement from the banking and insurance department. Some of the underpayments, which took place between 1996 and 2006, were made by other insurance companies that were later acquired by Health Net. Penalties included $2 million in reimbursement for the state’s investigation.

The company in late 2002 had paid more than $800,000 in restitution to New Jersey members after an earlier complaint. The department launched a new investigation after learning that underpayments by the company and two predecessor companies had begun earlier than the company had disclosed.

Health Net shares closed down 34 cents, or 1 percent, to $26.58 in Tuesday trading on the New York Stock Exchange.