Sorry, but you are too late to request an extension for 2018 unless you are out of the country. You had to request an extension by April 15, 2019, Now your 2018 tax return is just late. If you are getting a refund there is no penalty for filing after the deadline. If you owe tax due, then get your return prepared and filed as soon as you can, since your penalty/interest have begun to add up. TurboTax will not calculate that for you--expect a bill from the IRS based upon how much you owed and when they receive your payment.