April 15 is the deadline for the first quarterly estimated tax payment for 2021, if you’re required to make one. You may have to make estimated tax payments if you receive interest, dividends, alimony, self-employment income, capital gains, prize money or other income. If you don’t pay enough tax during the year through withholding and estimated payments, you may be liable for a tax penalty on top of the tax that’s ultimately due. Four due dates Individuals must pay 25% of their “required annual payment” by April 15, June 15, September 15, and January 15 of the following year, to avoid an underpayment penalty. If one of those dates falls on a weekend or holiday, the payment is due on the next business day. The required annual payment for...