Which of the Following Statements About Estimated Tax Payments and Underpayment

Which of the following statements about estimated tax payments and underpayment penalties is true for individual taxpayers?

A) Taxpayers who have paid their full tax liability by the original tax return due date are protected from underpayment penalties.
B) Taxpayers who have uneven income streams can pay estimated tax quarterly in uneven amounts and not be susceptible to underpayment penalties.
C) Taxpayers who have paid their required amount of estimated tax, even though not on time, are protected from underpayment penalties.
D) Taxpayers who have paid their full tax liability by the extended tax return due date are protected from underpayment penalties.