400.3-308. (a) In an action with respect to an instrument,the authenticity of, and authority to make, each signature on theinstrument is admitted unless specifically denied in thepleadings. If the validity of a signature is denied in thepleadings, the burden of establishing validity is on the personclaiming validity, but the signature is presumed to be authenticand authorized unless the action is to enforce the liability ofthe purported signer and the signer is dead or incompetent at thetime of trial of the issue of validity of the signature. If anaction to enforce the instrument is brought against a person asthe undisclosed principal of a person who signed the instrumentas a party to the instrument, the plaintiff has the burden ofestablishing that the defendant is liable on the instrument as arepresented person under Section 400.3-402(a).
(b) If the validity of signatures is admitted or proved andthere is compliance with subsection (a), a plaintiff producingthe instrument is entitled to payment if the plaintiff provesentitlement to enforce the instrument under Section 400.3-301,unless the defendant proves a defense or claim in recoupment. Ifa defense or claim in recoupment is proved, the right to paymentof the plaintiff is subject to the defense or claim, except tothe extent the plaintiff proves that the plaintiff has rights ofa holder in due course which are not subject to the defense orclaim.
(L. 1992 S.B. 448)