As a self-employed individual, generally you are required to file an annual return and pay estimated tax quarterly.
Self-employed individuals generally must pay self-employment tax (SE tax) as well as income tax. SE tax is a Social Security and Medicare tax primarily for individuals who work for themselves. It is similar to the Social Security and Medicare taxes withheld from the pay of most wage earners. In general, anytime the wording "self-employment tax" is used, it only refers to Social Security and Medicare taxes and not any other tax (like income tax).
Before you can determine if you are subject to self-employment tax and income tax, you must figure your net profit or net loss from your business. You do this by subtracting your business expenses from your business income. If your expenses are less than your income, the difference is net profit and becomes part of your income on page 1 of Form 1040. If your expenses are more than your income, the difference is a net loss. You usually can deduct your loss from gross income on page 1 of Form 1040. But in some situations your loss is limited. See Pub. 334, Tax Guide for Small Business (For Individuals Who Use Schedule C or C-EZ) for more information.