To avoid interest on penalties, the IRS requires tax payers to pay estimated tax payments throughout the year. For many individuals this is accomplished by filing out a W4 for their employer and having income tax withholding on their paychecks.
When additional income (like Form 1099) is earned, it can become more complicated. You would need to track income and expenses throughout the year to have a reasonable idea of the net taxable income plus self employment tax. If that is not feasible, one can simply estimate the tax based upon the gross earnings throughout the year that will be reported on the 1099.
Once the taxes are estimated, they need to be paid quarterly.
Other resources you may be interest in:
Estimated Taxes
Self Employment Tax Calculators
IRS Direct Pay
