If the department of revenue was not satisfied with the amount I paid through TurboTax, why would they accept my tax return in the first place? That is not how it works ... the accept the return for processing and once they processed the return the penalty/interest is issued.
Why would they send me this notice months later by mail with no information about why I owe more? The bill should have an explanation. They can charge you interest if you did not pay enough timely.
They are charging me interest but offer no explanation on why I owe money, and their website is down so I can't even pay it to stop the interest from accumulating. Try again tomorrow or Monday... often systems are updated over holiday weekends.