Does anyone know until when I have to file my taxes if i filed for an extension?

[DoninGA]

The 2018 tax return with extension has to be filed on or before October 15, 2019 or there will be a failure to file penalty assessed.

Any taxes owed on the 2018 tax return were due and payable on April 15, 2019.  An extension request does not extend the time to pay taxes owed.