YES. If you fail to file online (if your state has this ability) or postmark your return by the posted filing date, there is both a penalty and interest that need to be included when you DO file.
PENALTY: this is $50 or 10% of the final amount that you owed for that quarter originally (whichever is the GREATER NUMBER)
INTEREST: In addition, you must add .417% per month that you are late to the amount owed to each jurisdiction that you owed. (this number is based on the current annual percentage rate of 5% set by the government divided by 12 months.) Prior to July 1, 2013, the annual percentage rate was 12% annually (or 1% per month.)
If you were getting a refund from a particular jurisdiction, or did not owe anything to a particular jurisdiction, then you do NOT owe that jurisdiction INTEREST, but you still have the PENALTY portion to pay on the return as a whole.
Note: OUR WEB SITE CALCULATES THIS AUTOMATICALLY FOR YOU FOR ALL MEMBER ACCOUNTS! You can even run scenarios to see what the penalty would be based on when you think you may file.