“Section 1699 of the Civil Code provides: “The destruction or cancellation of a written contract, or of the signature of the parties liable thereon, with intent to extinguish the obligation thereof, extinguishes it as to all the parties consenting to the act.” A related rule is set forth in Civil Code section 1700: ‘The intentional destruction, cancellation, or material alteration of a written contract, by a party entitled to any benefit under it, or with his consent, extinguishes all the executory obligations of the contract in his favor, against parties who do not consent to the act.’ The ‘executory obligations’ that are extinguished under section 1700 are all of the unperformed or partially unperformed obligations created by the contract in question. If the executory function of the document has ceased, an alteration is of no consequence. For example, an alteration in a recorded deed at a time following its recordation does not affect the validity of the document because the title passed as a result of the deed at the time of delivery.”
[California Affirmative Defenses [certain citations omitted]]
