FAQ: Should I be paying estimated tax or having more withheld instead?
Some individuals must pay estimated taxes or face a penalty in the form of interest on the amount underpaid. Self-employed persons, retirees, and nonworking individuals most often must pay estimated taxes to avoid the penalty. But an employee may need to pay them if the amount of tax withheld from wages is insufficient to cover the tax owed on other income. The potential tax owed on investment income also may increase the need for paying estimated tax, even among wage earners.