Unless you tell TurboTax not to, TurboTax does, by default, calculate the interest penalty based on the amounts and dates of your estimated tax payments and includes Form 2210 with your filed tax return. However, your tax-payment entries may not agree with the details that the IRS has, or the IRS may find some income omitted from your tax return, so the result calculated by the IRS may be different. The IRS then bills for or refunds the difference.
