September 15, 2021, is the deadline for third quarter estimated tax payments. This generally applies to people who are self-employed and some investors, retirees and those who may not normally have taxes withheld from their paycheck by their employers. The U.S. tax system operates on a pay-as-you-go basis. This means taxpayers are to pay most of their tax during the year, as they earn or receive income. Therefore, individuals not subject to withholding may need to make quarterly estimated tax payments. If a taxpayer underpaid their taxes, they may have to pay a penalty. This applies whether
