If you filed but didn't pay, there's interest being compounded daily on what you owe, which is the quarterly federal short term tax rate, plus 3%. As of this writing, the IRS is charging 8% per year. In addition to interest, you're also being charged a Failure-to-Pay Penalty, which is .5% of the tax owed for each month. There is no maximum for the failure-to-pay penalty. If you're sent a number of notices from the IRS and you still don't pay, the penalty increases to 1%.
***Bryson Law Firm, LLC is a Louisiana law firm focusing 100% of our practice on helping people and businesses solve their IRS and Louisiana state tax problems. We have offices in Lafayette, Baton Rouge, and Shreveport.