I filed extension for 2018 but didn't file taxes by oct 2018 deadline. Do I owe a penalty?

[reim]

I filed an extension by 4/15/18 and paid IRS more than what was due (15k was due, but I paid 20k with my extension) . I got notification that my extension and payment was processed by IRS. However, I couldn't file my taxes by the Oct 2018 deadline. I'm now using TurboTax 2018 CD to mail in my state and federal returns. IRS and state owes me money after I made that extra payment on 4/15. Will they charge me a Late Filing and or Late Payment fine penalty? If so how do they calculate that? 

Please any help is much appreciated. 

[LeonardS]

The IRS penalties for filing taxes late is usually 5% of the tax owed for each month, or part of a month, that your return is late up to five months (25%). If your return is over 60 days late, the minimum penalty for late filing is the smaller of $100 or 100 percent of the tax owed.

In your situation, you file your taxes that are late you do not owe taxes so no penalty should be applied.

You should receive interest on the amount of your overpayment from the payment date 04/15/2018 through the date the IRS processes your 2018 tax return.