...for 2018 taxes, you will still have to pay your full estimated taxes due for the 2018 tax filing by 15 Apr 2019....even if you get an extension. You pay at the time you file the extension IF you don't pay with the extension application, then any balance due that shows up on 15 Oct will get 6 months of penalty and interest assessed, even with the extension.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
