(a) A party may amend its pleading once without permission at any time before the period for responding expires or, if no responsive pleading is required, within 20 days after service of the pleading.

(b) Consistent with CPLR 3025, a party may amend its pleading at any time prior to the final order of the commissioner by permission of the ALJ or the commissioner, and absent prejudice to the ability of any other party to respond.