Automatic 2-month Extension of time to file and pay-Working overseas

[artp]

Taxpayer, US citizen and CA resident is currently working in Africa from Jan-Jun of this year and wants to file an extension to file and pay his federal taxes. The instructions in Pub 54 state that to qualify you must be living outside of the US on the due date of your return so he would seem to qualify. He is expected to owe about $15,000 and does not meet any of the normal exceptions for avoiding underpayment penalties (paying amount equal to last years tax or 90% of current year)

Question: Because he qualifies for this special extension will the normal underpayment penalties and interest still apply?  Even if he manages to pay the full $15,000 by June 15, 2019?

[Gail in Virginia]

This is an extension of time to file AND pay unlike a regular extension.  However, the interest still begins on April 15 and I don't think this waives the penalty for being under-withheld, only the penalty for paying after April 15.  The penalty for late payment would begin June 15 for an overseas taxpayer.  At least that is my understanding.

[artp]

5 hours ago, Gail in Virginia said:

This is an extension of time to file AND pay unlike a regular extension.  However, the interest still begins on April 15 and I don't think this waives the penalty for being under-withheld, only the penalty for paying after April 15.  The penalty for late payment would begin June 15 for an overseas taxpayer.  At least that is my understanding.

Thanks, Gail