Estimated tax is the method used to pay tax on income that is not subject to withholding. This income includes earnings from self-employment, interest, dividends, rents, and alimony, unemployment compensation and the taxable part of Social Security benefits. For tax year 2018, the remaining estimated tax payment due dates are Sept. 17 and Jan. 15, 2019. You can pay your taxes throughout the year anytime. You must select the tax year and tax type or form when paying electronically. Filers paying by check should make it out to the “United States Treasury” and indicate the tax year and type of taxes they are paying.