If you are getting a refund there is not a penalty for filing after the April 15 deadline. If you owed tax due, then you are subject to penalty and interest if you filed after the deadline. The IRS will calculate it and bill you if that is the case. TurboTax does not calculate that for you because it is based on when the IRS receives the return and your payment, and upon how much was owed on the tax return.
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