Md. Code, Insurance § 15-222

(a) A policy of health insurance may contain the following provision:

“Insurance with other insurers: If there be other valid coverage, not with this insurer, providing benefits for the same loss on a provision of service basis or on an expense incurred basis and of which this insurer has not been given written notice prior to the occurrence or commencement of loss, the only liability under any expense incurred coverage of this policy shall be for such proportion of the loss as the amount which would otherwise have been payable hereunder plus the total of the like amounts under all such other valid coverages for the same loss of which this insurer had notice bears to the total like amounts under all valid coverages for such loss, and for the return of such portion of the premiums paid as shall exceed the pro rata portion for the amount so determined. For the purpose of applying this provision when other coverage is on a provision of service basis, the ‘like amount’ of such other coverage shall be taken as the amount which the services rendered would have cost in the absence of such coverage.”

(b) The phrase “-- Expense incurred benefits” shall be added to the caption of the provision set forth in subsection (a) of this section if the provision is included in a policy that contains the policy provision set forth in § 15-223 of this subtitle.

(c) (1) A benefit provided for the insured under a compulsory benefit statute, including a workers’ compensation or employer’s liability statute, whether provided by a governmental unit or otherwise, shall be considered “other valid coverage” of which the insurer has had notice.

(2) The insurer may include in the provision set forth in subsection (a) of this section a definition of “other valid coverage” if the definition:

(i) is approved as to form by the Commissioner; and

(ii) is limited to:

1. coverage provided by organizations subject to regulation by insurance law or insurance authorities of this State, another state, or a province of Canada;

2. coverage provided by hospital or medical service organizations; and

3. any other coverage that the Commissioner may approve for inclusion.

(3) Unless defined otherwise, “other valid coverage” does not include:

(i) group insurance or automobile medical payments insurance;

(ii) coverage provided by hospital or medical service organizations; or

(iii) coverage provided by union welfare plans or by employer or employee benefit organizations.

(4) “Other valid coverage” may not include third party liability coverage.