WHAT IS THE PENALTY FOR UNDERPAYMENT OF ESTIMATE TAX?

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The underpayment penalty is not a set amount. IRS Form 2210 (or 2210-F) is used to calculate the penalty. TurboTax automatically fills out Form 2210 for you if we determine that you didn't pay sufficient income tax during the tax year. The penalty is already accounted for in your balance due or refund amount.

Please see the FAQ below for more information.

What is Form 2210 or 2210-F?  https://ttlc.intuit.com/replies/3300251