402.209 Modification, rescission and waiver.
(1) An agreement modifying a contract within this chapter needs no consideration to be binding.
(2) A signed agreement which excludes modification or rescission except by a signed writing cannot be otherwise modified or rescinded, but except as between merchants such a requirement on a form supplied by the merchant must be separately signed by the other party.
(3) The requirements of s. 402.201 must be satisfied if the contract as modified is within its provisions.
(4) Although an attempt at modification or rescission does not satisfy the requirements of sub. (2) or (3) it can operate as a waiver.
(5) A party who has made a waiver affecting an executory portion of the contract may retract the waiver by reasonable notification received by the other party that strict performance will be required of any term waived, unless the retraction would be unjust in view of a material change of position in reliance on the waiver.
Not every contract for the sale of goods over $500, nor every modification thereof, strictly complies with the requirements of the statute of frauds, and it would be unreasonable to declare categorically all such contracts unenforceable. The UCC and Wisconsin case law recognize exceptions to the statute of frauds, including waiver and performance. An attempt at modification contemplates a completed oral modification of a written contract that prohibits oral modification. The inquiry into whether there has been an attempt at modification sufficient to operate as a waiver of the statute of frauds is closely related to the inquiry to determine whether there was a valid oral modification. Royster-Clark, Inc. v. Olsen's Mill, Inc. 2006 WI 46, 290 Wis. 2d 264, 714 N.W.2d 530, 03-1534.
A dealership agreement is primarily for the sale of goods, making this section applicable. American Suzuki Motor Corp. v. Bill Kummer, Inc. 65 F.3d 1381 (1995).