§ 15-a. Assessment on insolvent group self-insured trusts. The legislature finds that in lieu of the assessments under sections fifteen and one hundred fifty-one of this chapter that shall no longer be imposed on closed group self-insured trusts as a result of the chapter of the laws of two thousand eleven which added this section, the members of group self-insured trusts that were insolvent upon closing, and that fail to pay their obligations within the periods specified by this section, shall be subject to a one time assessment pursuant to this section. Within thirty days of January first, two thousand sixteen, all employers who were members of a closed group self-insured trust that was insolvent at the time the group was closed shall be subject to an assessment under this section, except for those employers that: (1) have entered into a settlement agreement or payment plan with the board under which they have agreed to resolve all liabilities from the membership in such trust, and remain current in their payments; (2) are members of a group self-insurer that has transferred all of its liabilities transferred via a loss portfolio transfer; or (3) have paid all moneys billed them by the board at the time such assessment is due. For purposes of this section, insolvent means the inability of a private group self-insured trust to pay its outstanding lawful obligations under this chapter as they mature in the regular course of business, as may be shown by: (i) the self-insurer being underfunded as defined in subdivision three-a of section fifty of this chapter; and (ii) the sum of the group self-insured trust's assets, as defined by regulation of the chair, plus the available security deposit held by the chair pursuant to subdivision three-a of section fifty of this chapter and regulation of the chair, being less than the total cost of all of the group self-insured trust's anticipated workers' compensation liabilities, as defined by board regulations, that will accrue within the succeeding six months. The total of such assessment shall be determined by the percentage of the assessment levied on all employers under subdivision eight of section fifteen of this article in two thousand ten that was levied on group self-insured trusts multiplied by the total amount of the employer's unpaid pro rata share of any deficit owed by the closed group self-insured employer of which such employer was a member, as determined by the chair. The amount received on such assessment shall be used as an offset against the assessments imposed on other employers under subdivision eight of section fifteen of this article and section one hundred fifty-one of this chapter in the calendar year following the year in which it was received.