(1) An administrative judge before whom a proceeding is pending may join, or any party to such proceeding may request the administrative judge to join, as a party, on written notice and a right to be heard, an insurer, employer, or other person who may be liable for payment of compensation to the claimant.(2) A party to be joined shall not be allowed to raise a defense of late claim if the original claim was filed timely, but shall be allowed to raise any and all other reasonable defenses which would have been available to him had the claimant filed an original claim against the party to be joined, provided that the party requesting joinder, in the absence of mistake or inadvertence, made a reasonable attempt to ascertain the identity of the correct party or parties before the filing of the original claim.(3) When it is decided, after proper hearing of a request to join, that the subject of such request shall be joined, the new party shall be allowed a reasonable period of time to prepare a defense. Such period shall not exceed 45 calendar days from the date of joinder, unless the administrative judge who orders the joinder finds that additional time to prepare a defense is needed.Amended by Mass Register Issue 1331, eff. 1/27/2017.