Taxpayers fill out quarterly Internal Revenue Service Form 1040-ES estimated tax vouchers with their name, address, Social Security number and the amount of the payment they enclose, reports About.com. To calculate the amount of their estimated payment, taxpayers can use an IRS worksheet that accompanies Form 1040-ES or a tax software program. They mail the voucher to the IRS along with a check or money order for the payment amount.
If they are married and file taxes jointly, taxpayers fill in their spouse's information on Form 1040-ES as well, even if the spouse is not involved in the income-generating business, explains About.com. Estimated tax payments for self-employed individuals take the place of the amounts that employers usually withhold from pay checks. As of 2015, self-employed people must fill in Form 1040-ES vouchers and pay estimated taxes if they expect to pay $1,000 or more in yearly federal taxes. The payments are due in April, June, September and January.
Income subject to quarterly estimated tax payments includes payments people receive as freelancers or independent contractors, rental income, alimony payments and interest income, according to About.com. Estimated tax payments for self-employed individuals must include income tax and self-employment tax. Self-employment tax consists of 15.3 percent of income, which includes 12.4 percent for Social Security and 2.9 percent for Medicare.