Maryland Commercial Law Section 22-303

      (a)      An agreement modifying a contract subject to this title needs no consideration to be binding.

      (b)      An authenticated record that precludes modification or rescission except by an authenticated record may not otherwise be modified or rescinded. In a standard form supplied by a merchant to a consumer, a term requiring an authenticated record for modification of the contract is not enforceable unless the consumer manifests assent to the term.

      (c)      A modification of a contract and the contract as modified must satisfy the requirements of §§ 22-201(a) and 22-307(g) of this title if the contract as modified is within those provisions.

      (d)      An attempt at modification or rescission which does not satisfy subsection (b) or (c) of this section may operate as a waiver if § 22-702 of this title is satisfied.