Conn. Gen. Stat. § 12-517: Extension of time for filing return and paying tax.

The commissioner may for reasonable cause extend the time for the filing of any return due under this chapter and the payment of tax due thereon under such rules and regulations as he shall prescribe. Said commissioner may require the filing of a tentative return and the payment of an estimated tax. Any additional tax which may be found to be due on the filing of a final return as allowed by such extension shall bear interest at the rate of one and one-fourth per cent per month or fraction thereof from the original due date of such tax to the date of actual payment.