Mass. Gen. Laws ch. 176G, § 15

Each health maintenance organization shall furnish to the commissioner evidence of a surety bond in an amount satisfactory to the commissioner or deposit with the commissioner cash or sureties acceptable to him in at least the same amount as a guarantee that the obligation to the enrollees will be performed. The commissioner may waive this requirement if a health maintenance organization has contracted with a carrier as defined in section one for the purpose of reinsurance.