Section 26. Every professional fund raising counsel, commercial co-venturer, professional solicitor, and charitable organization required to have a certificate of registration under section nineteen, shall, in accordance with the rules and regulations prescribed by the division, keep true fiscal records as to such activities within the commonwealth as may be covered by sections eighteen to thirty-five, inclusive, in such form as will enable them accurately to provide the information required by said sections. Upon demand such records shall be made available to the division for inspection. Such records shall be retained for a period of at least three years after the end of the period of registration to which they relate.