452 CMR, § 1.04
Subject to the provisions of M.G.L. c. 152, § 7(1) and 8(1), as to newly discovered evidence, no grounds for refusal to pay compensation shall be allowed as a defense unless the insurer's notice of refusal contains a statement of the factual basis supporting such grounds. No ground or factual basis sought to be raised by an insurer on newly discovered evidence shall be allowed as a defense unless the insurer reports each such ground or factual basis to the injured employee and the Department not less than five working days before any conference or hearing, provided that if such evidence is not in fact discovered until a time within such five day period, a continuance may be granted at the judge's discretion if requested by the insurer at the conference or hearing.
452 CMR, § 1.04