Federal and state tax laws require a quarterly payment of estimated taxes due from corporations, trusts, estates, non-wage employees, and wage employees with income not subject to withholding. Individuals must remit at least 100 percent of their prior year tax liability or 90 percent of their current year tax liability in order to avoid an underpayment penalty. Corporations must pay at least 90 percent of their current year tax liability in order to avoid an underpayment penalty. Additional taxes due, if any, are paid on taxpayer's annual tax return.
Typically, non-wage earners pay estimated tax since their incomes are not subject to withholding tax to the same extent as the income of a salaried worker. Persons who receive a certain level of additional income, apart from their salaries, must also pay estimated tax.
The calculation and payment of estimated tax are preliminary stages to the filing of a final income tax return. Under federal and most state laws, estimated tax is paid in quarterly installments. The tax paid is applied to the tax owed when the taxpayer files a final return. Any overpayment of estimated tax will be refunded after the filing of the final return. If no tax is owed, a taxpayer is still required under federal law, and many state laws, to file a final return. When tax is due upon the filing of the final return, the taxpayer must pay the outstanding amount. Depending upon the amount due and the reasons for the miscalculation, a taxpayer might be liable under federal and state law for interest imposed upon the deficiency, as well as being subject to a penalty.