You can go here https://turbotax.intuit.com/irs-tax-extensions/ to file a federal extension for your 2016 return. Keep in mind, filing an extension gives you until October 16 to file, but it doesn't give you until October to pay your taxes, if you owe. Those are still due by midnight, April 18.
Do I need to file an extension if I'm getting a refund?
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