The Commissioner for good cause shown may extend for no more than 30 days the time for filing a tax return or paying any amount required to be paid with any return. The extension may be granted at any time, provided that a request therefor is filed with the Commissioner within or prior to the period for which the extension may be granted. Any taxpayer to whom an extension is granted shall pay, in addition to the tax, interest at the rate of 1 percent per month or fraction thereof until the date of payment.