The federal government requires sole proprietors to file quarterly taxes. If you are the sole owner of an unincorporated business, you need to pay taxes by the federal quarterly deadlines. Landlords or other types of investors may also be required to file quarterly taxes. Generally, if you will not have enough withheld from your income to meet your tax liability at the end of the year, you may need to file quarterly taxes.

Quarterly taxes are filed at the federal level four times a year on: 

- April 15^th 
- June 15^th
- September 15^th 
- January 15^th

When these dates fall on legal holidays, Saturdays, or Sundays, quarterly taxes are due on the next business day.

The federal tax form to file quarterly taxes is called a 1040-ES, and is available at http://www.irs.gov/pub/irs-pdf/f1040es.pdf. Form 1040-ES is also available in local IRS offices or by calling 1-800-TAX-FORM. This form includes information on how to figure out the amount of estimated quarterly taxes you owe. IRS Publication 505 (Chapter 2) has additional information on federal estimated taxes.           

You may also be required to pay state quarterly taxes. Usually, the state deadlines to file quarterly taxes are the same as or similar to federal deadlines. The Federation of Tax Administrators (FTA) Web site has links to tax information for each state. Click on your state to get information and forms for filing state quarterly taxes. The state quarterly tax requires a different form, not the federal tax form 1040-ES.

Make sure you pay your quarterly taxes on time and that you calculate the amount correctly. The IRS may penalize you for late or incorrect payment. It may be worth hiring an accountant to calculate these payments for you.