Banks are required to keep records of all accounts for a minimum of 5 years by law. Some banks may keep records longer, especially if they are electronic.
In the event that personal banking records have been lost, banks have records of accounts and transactions for years. Depending on the bank, and whether it's a state or federal bank or a credit union, the records for each individual account can be kept for varying amounts of time, with a minimum of 5 years after closing the account. However, for different accounts and different purposes, like mortgages and loans, the banks have a different standard for record retention.
It is highly suggested that each person retain their own personal records for up to 10 years after the accounts at a bank are closed. This is also highly regarded as a safe minimum for any tax records as well. Any records that may involve a government entity should be kept for at least a minimum of 2 years, if not longer, in the case of an audit or in the rare case of the bank not maintaining the records through theft or software issues. When an individual has a credit card through a bank, the account only needs to become dormant in order for the ban to consider it closed, but these records must be retained for 5 years after closing or dormancy as well.