Oct 15th midnight

10-15-2019 in YOUR time zone.

Your extension gave you extra time to prepare your 2018 tax return documents.  It did not give you extra time to pay.  If you did not pay your estimated 2018 tax due by April 15, 2019 then when the IRS receives your 2018 return and your payment, they will calculate your penalty/interest and bill you later.  TurboTax will not calculate the penalty or interest.

You have until October 15, 2019 to e-file your 2018 tax return.  After that, e-filing for 2018 will be shutting down, and a 2018 return will have to be printed, signed and mailed instead.  The online software will also be shutting down, so if you are not finished preparing your 2018 return by then, you will have to download desktop software to a full PC or Mac to finish the return.

When you requested your extension you were supposed to pay your estimated tax due.  Did you enter the payment you made into your tax return?  Go to Federal>Deductions and Credits>Estimates and Other Taxes Paid>Other Income Taxes  This will show up on line 17 of your Form 1040

Just trying to help and provide information many users need.  But no good deed goes unpunished.

Thank you for the information.  I found it informative and useful.

I was given a refund from 2018 turbo tax.   do not know what you are talking about

@bw184586 You have three posts in this thread.  Two of them are blank.  One of them says you do not know what we are talking about---or that you got a refund for 2018.

Do you have a question that you want us to answer?

Please i do not know what you are saying  Have no knowledge of an extenion in 2018

@bw184586 Then WHY do you keep posting to this thread?  What are you trying to do?   This is now your fourth post--for seemingly no reason.