Md. Code Ann., Health Occ. § 1-304
(a) A health care practitioner shall disclose the name of a referring health care practitioner on each request for payment or bill submitted to a third party payor, including nonprofit health plans and fiscal intermediaries and carriers, that may be responsible for payment, in whole or in part, of the charges for a health care service, if the health care practitioner knows or has reason to believe:
Added by Acts 1993, c. 376, § 2, eff. Oct. 1, 1993.