Individuals: Filing Extensions & Estimated Tax Payments
Extensions: Pay online & get the extension at the same time, no separate filing required.
Federal - IRS
The link takes you to the IRS webpage to pick your payment type. The picture below shows the pertinent part of the webpage – click direct pay (free, enter bank acct & routing number) or credit or debit card (fees apply).
From there, pick from the drop down list – Extension (2017) or Estimated Tax Payment (2018).
Picture is for reference - Links do not work:
NC Estimated Tax Payment