P.R. Laws tit. 19, § 657
(a) Alteration. — Means: (i) an unauthorized change in an instrument that purports to modify in any respect the obligation of a party, or (ii) an unauthorized addition of words or numbers or other change to an incomplete instrument relating to the obligation of a party.
(b) Except as provided in subsection (c) of this section, an alteration fraudulently made discharges a party whose obligation is affected by the alteration unless that party assents or is precluded from asserting the alteration. No other alteration discharges a party, and the instrument may be enforced according to its original terms.
(c) A payor bank or drawee paying a fraudulently altered instrument or a person taking it for value, in good faith and without notice of the alteration, may enforce rights with respect to the instrument: (i) according to its original terms, or (ii) in the case of an incomplete instrument altered by unauthorized completion, according to its terms as completed.
History —Aug. 17, 1995, No. 208, § 2-407; Aug. 31, 1996, No. 176, § 2.