Probably for late fees and interest since an extension only gives you extra time to get your paper work together and FILE. Any any tax due must have been paid by the due date of the return which was July 15 of 2019. Late fees and interest started after July 15. An extension does NOT extend the date to pay, so yes, you must pay it.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
