It shall be the duty of every person engaging or continuing in this state, in any business as defined in this chapter, and for which the privilege tax is imposed by this chapter, to keep and preserve adequate records of all transactions by which securities of any character are required, evidencing liens upon tangible property located in this state, as hereinbefore defined. The records provided for in this section shall be kept in the taxpayer’s principal place of business within this state, and if no such principal place of business is maintained in this state, then such records shall be kept at some convenient place in the custody of some reliable officer or person to be designated by the commissioner. Said records shall be open to inspection by the commissioner or his duly authorized agents at all reasonable times, for the purpose of ascertaining the amount of taxes due under this chapter.