Insurers, including the State Workers' Insurance Fund, are authorized to provide, on a voluntary basis, to sole proprietors, partners of a partnership or members of a limited liability company, workers' compensation insurance equivalent to that which employers provide to employes which insure their liability under Article III.¹ For the purposes of computing the premium charge, the wages of a sole proprietor, partner or member shall be at least equal to the minimum payroll for a corporate officer, and no more than the maximum payroll for a corporate officer, as established by underwriting rules approved by the Insurance Department. If an injury is compensable under the terms of this coverage, it shall be a rebuttable presumption that the wages of the injured individual are at least equal to minimum payroll for a corporate officer for the purposes of calculating his average weekly wage and paying benefits under sections 306 and 307.²