What are the implications of a bank's failure to report a forged or altered check?

[39 Cal.App.4th 1072] Plaintiffs argue that this case is governed by the decisions in Bullis v. Security Pac. Nat. Bank (1978) 21 Cal.3d 801, 148 Cal.Rptr. 22, 582 P.2d 109 and Danning v. Bank of America, supra, 151 Cal.App.3d 961, 199 Cal.Rptr. 163. We do not find either Bullis or Danning to be applicable. In Bullis, the defendant bank was held liable for permitting one co-executor of an estate to withdraw money from the estate's account although pursuant to statute, contract and the common law the signatures of both co-executors should have been required. (21 Cal.3d at pp. 807, 811, 148 Cal.Rptr. 22, 582 P.2d 109.) In Danning, the defendant bank erroneously paid a check which neither had nor purported to have an authorized signature thereon and the bank's error was discovered and reported almost immediately. (151 Cal.App.3d at pp. 968-969, 199 Cal.Rptr. 163.) Neither of these decisions involved the payment of a forged or altered check and neither was concerned with a customer's failure to discover and report promptly a forgery or alteration.