Interest will be charged on any late filing or late payment penalty from the original due date of the return to the date paid. In addition, if other penalties are not paid within 15 days, interest will be charged from the date of the billing notice until the date of payment.
Interest compounds daily and the interest rate is adjusted twice a year.
An underpayment penalty will be assessed when taxes are not paid by the due date. A delinquent penalty will be assessed on unpaid taxes if a return is filed late. There are also other penalties that can be imposed for a check returned for insufficient funds, negligence, substantial understatement of tax and fraud.