Get your taxes done using TurboTax

Here's a link from the IRS, which indicates either the tax filing due date, or the quarterly due date for estimated payments. 

How we calculate the penalty

We calculate the amount of the Underpayment of Estimated Tax by Individuals Penalty based on the tax shown on your original return or on a more recent return that you filed on or before the due date. The tax shown on the return is your total tax minus your total refundable credits.

We calculate the penalty based on:

• The amount of the underpayment
• The period when the underpayment was due and underpaid
• The published quarterly interest rates for underpayments

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