@massachusetts1 Sorry the interest will be calculated from the original due date in May. The extension is only to file the return. Any tax due was still due by April 15 or May. Did you enter the estimates paid and any payment you made with the extensions?
Even if you are getting a refund you can still owe a penalty for not paying in evenly during the year. The IRS will bill you for any interest and penalties depending on when they get the tax due payment.
If Turbo Tax calculates a penalty you might be able to eliminate it or at least reduce it. You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you. It's form 2210.
It's under
Federal or Personal (for Home & Business Desktop)
Other Tax Situations
Additional Tax Payments
Underpayment Penalties - Click the Start or update button
