Oklahoma Real Estate Commission (OREC) has set a standard for transaction documents retention.
605:10-13-1. Duty to account; broker
Record retention. A broker shall maintain all records and files for a minimum of five (5) years after consummation or termination of a transaction. In the case of trust account records the five years shall commence with the date of disbursal of funds. Records as referenced in this paragraph shall be destroyed in a secure manner.
[See: attached OREC License Code and Rule Book]