The IRS penalties for filing taxes late is usually 5% of the tax owed for each month, or part of a month, that your return is late up to five months (25%). If your return is over 60 days late, the minimum penalty for late filing is the smaller of $100 or 100 percent of the tax owed.
In your situation, you file your taxes that are late you do not owe taxes so no penalty should be applied.
You should receive interest on the amount of your overpayment from the payment date 04/15/2018 through the date the IRS processes your 2018 tax return.
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