Okla. Stat. tit. 12A, § 12A-3-406: Negligence Contributing to Forged Signature or

Alteration of Instrument.

NEGLIGENCE CONTRIBUTING TO FORGED SIGNATURE

OR ALTERATION OF INSTRUMENT

(a) A person whose failure to exercise ordinary care

substantially contributes to an alteration of an instrument or to

the making of a forged signature on an instrument is precluded from

asserting the alteration or the forgery against a person who, in

good faith, pays the instrument or takes it for value or for

collection.

(b) Under subsection (a) of this section, if the person

asserting the preclusion fails to exercise ordinary care in paying

or taking the instrument and that failure substantially contributes

to loss, the loss is allocated between the person precluded and the

person asserting the preclusion according to the extent to which the

failure of each to exercise ordinary care contributed to the loss.

(c) Under subsection (a) of this section, the burden of proving

failure to exercise ordinary care is on the person asserting the

preclusion. Under subsection (b) of this section, the burden of

proving failure to exercise ordinary care is on the person

precluded.