And there are different methods to calculate it. You might have been able to reduce or eliminate it yourself when you filed. The IRS refigured it for you.
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
