Quarterly taxes are payable on April 15, June 15, September 15 and January 15 of the following tax year, notes the Internal Revenue Service (IRS). If a taxpayer fails to pay the proper amount of estimated tax by the end of each pay period, a penalty fee can be charged.
The date noted on the postmark is considered the date of payment. For due dates that fall on Saturdays, Sundays and legally recognized holidays payments are not considered late if made on the following day that is not a Saturday, Sunday or legally recognized holiday. A taxpayer does not have to start making quarterly payments until he starts earning an income that can be taxed, notes the IRS.