If you are currently outside the United States and Puerto Rico, you may qualify for an automatic two-month extension. See Extensions Outside U.S. and Puerto Rico for more information.
If you are likely to owe taxes, you still need to pay by the filing deadline to avoid late fees and penalties. You must estimate the tax due amount and pay when you file the extension request.
If you expect to receive a refund (i.e. your total 2021 payments are more than your estimated tax liability), the program will automatically enter zero (0) for your balance due on Line 6.