Estimated taxes

[DNT51]

I saw I had estimated taxes when I viewed my Federal return earlier in October. 

I had filed for an extension which I completed at that time.

I didn't know about the required estimated taxes until I  viewed my return at that time.

Will I have to pay any penalties since the due dates had already passed prior to my completing my taxes?

[xmasbaby0]

If you did not make a payment of your estimated tax due at the time that you requested an extension---by April 15-- then, yes you will be subject to paying interest on the amount owed.   You were supposed to pay your estimated tax due by April 15 even if you have had an extension to file.