Me. Stat. tit. 24-A § 2753
All insurers providing individual medical expense insurance on an expense-incurred basis providing payment or reimbursement for diagnosis or treatment of a condition or a complaint by a health care practitioner must accept the current standardized claim form for professional services approved by the Federal Government and submitted electronically. All insurers providing individual medical expense insurance on an expense-incurred basis providing payment or reimbursement for diagnosis or treatment of a condition or a complaint by a licensed hospital must accept the current standardized claim form for professional or facility services, as applicable, approved by the Federal Government and submitted electronically, and any claims for facility services must identify the physical location, including hospital off-campus locations, where services are provided. An insurer may not be required to accept a claim submitted on a form other than the applicable form specified in this section and may not be required to accept a claim that is not submitted electronically, except from a health care practitioner who is exempt pursuant to Title 24, section2985. All services provided by a health care practitioner in an office setting must be submitted on the standardized federal form used by noninstitutional providers and suppliers. Services in a nonoffice setting may be billed as negotiated between the insurer and health care practitioner. For purposes of this section, "office setting" means a location where the health care practitioner routinely provides health examinations, diagnosis and treatment of illness or injury on an ambulatory basis whether or not the office is physically located within a facility.
24-A M.R.S. § 2753