(b) In any city of this state having a population of one million or more, the overpayment rate referred to in paragraph (a) of this subdivision shall be set by the commissioner of taxation and finance pursuant to subsection (e) of section one thousand ninety-six of this chapter, or if no rate is set, at the rate of six percent per annum for the period from the date the application for refund in processible form is received by the commissioner of taxation and finance to a date preceding the date of the refund check by not more than thirty days. 2. The comptroller shall have general supervisory power over all county treasurers in respect to the duties imposed upon them by this article, and may make such rules and regulations, not inconsistent with this or any other statute, for the government of said county treasurers as he deems proper to secure a due accounting for all taxes and moneys collected or received and refunds and interest paid pursuant to any provision of this article.