Section 25. State officers, and members of departments receiving a salary or its equivalent, who are provided with offices by the commonwealth and whose duties require regular attendance at such offices, shall not be allowed or paid by the commonwealth any expenses in the nature of traveling or living expenses. Such officers or members of departments whose duties require them to travel elsewhere than to and from the offices provided for them by the commonwealth, and unpaid state officers or members of departments, and those whose duties do not require daily attendance and who receive compensation by the day, shall be allowed their actual reasonable expenses incurred in the performance of such duties, if such expenses are authorized by law to be paid by the commonwealth. Bills for such expenses shall be itemized and the dates when, and the purposes for which, such expenses were incurred shall be stated before their allowance by the comptroller.
In the case of allowable expenses incurred in the operation of private motor vehicles used in the performance of official duties, the maximum reimbursement shall not exceed a maximum established by the commissioner of administration. Said maximum shall be equivalent to the maximum reimbursement payable to state employees who are covered under a collective bargaining agreement for which an appropriation has been made by the general court. Said commissioner shall adjust said maximum, if such adjustment is required, on July first of each year and shall file a notice of such adjustment with the house and senate committees on ways and means at least ninety days prior to said date.