Registered users including businesses attach a one-time-use identity verifier to as many financial and other transactions as they choose to protect themselves from identity thieves. They may also attach a security message to any identity verifier to ensure that a thief cannot steal a registered user's check from a mailbox and use the unused identity verifier. By using one list for all of a person's transactions, applications for new credit by identity thieves are also prevented. All of this is made possible by allowing the identity verifiers to be approved nonsequentially.