Independent contractors report their income on Form 1040, Schedule C (PDF), Profit or Loss from Business (Sole Proprietorship), or you may qualify to use Form 1040, Schedule C-EZ (PDF), Net Profit from Business (Sole Proprietorship). You should also be aware of Form 1040, Schedule SE (PDF), Self-Employment Tax, which must be filed if net earnings from self-employment are $400 or more. This form is used to figure your social security and Medicare tax which is based on your net self-employment income. You may also need to file Form 2210 (PDF), Underpayment of Estimated Tax by Individuals, Estates & Trusts, if you do not make estimated tax payments.

References:

• Form 1040, Schedule C (PDF), Profit or Loss from Business (Sole Proprietorship)
• Form 1040, Schedule C-EZ (PDF), Net Profit from Business
• Form 1040, Schedule C Instructions
• Form 1040, Schedule SE (PDF), Self-Employment Tax
• Form 1040, Schedule SE Instructions
• Publication 334, Tax Guide for Small Business
• Tax information for Business
• Form 2210 (PDF), Underpayment of Estimated Tax

Source: www.irs.gov