The state tax commission at its discretion may furnish to the multistate tax commission, any information contained in tax returns and reports and related schedules and documents filed pursuant to the laws of this state and in the report of an audit or investigation made with respect thereto, provided only that said information be furnished solely for tax purposes; and the multistate tax commission may make said information available to the tax officials of any other state, the District of Columbia, the United States and its territories for tax purposes.