1. Estimated Tax Payments: If you are a sole proprietor, a partnership, or a shareholder in a Sub-chapter S corporation, you are considered self-employed. Since you don't have an employer deducting taxes from your pay throughout the year, you are responsible for making advance payments of your estimated federal income tax. Estimated tax payments are due quarterly - on April 15, June 15, September 15, and January 15 - and are filed on a Form 1040-ES. At the end of the tax year, you will file a final Form 1040 with a Schedule C, which itemizes your business expenses for the whole year.

To avoid underpayment penalties - which are substantial - individuals whose adjusted gross incomes were under $150,000 need to have paid at least 100 percent of their prior year's tax bill. People whose incomes were over $150,000 need to have paid 110 percent of the amount they owed in the prior year.

It's in your interest to make your estimated tax payments during the year. This system also keeps you from owing a large sum of money all at once, which can be overwhelming. If your state of residence has income taxes, as most do, you will have to make estimated tax payments throughout the year for state taxes as well.

2. Self-Employment Tax: Your estimated tax payments will also include the federal self-employment tax - Social Security and Medicare. If you were employed by someone else, your employer would pay half of your Social Security and Medicare and the other half would come out of your paycheck. Self-employed people must pay the full amount themselves; however, 50 percent of the self employment tax is deductible on the 1040 form.

What if you are a salaried employee and you operate a home-based business as a sideline? In this case, you'll be filing both the usual Form 1040 and a Schedule C for your home business deductions; you may also have to pay additional self-employment tax. No matter how little your sideline income is, you should be aware that it is subject to tax - although by taking advantage of the home-office deduction, you may find you owe little or no taxes.

3. Employment Taxes: Home-based workers who employ others must comply with many additional tax requirements. IRS Circular E, Employer's Tax Guide, covers the federal regulations, and your state tax agency can inform you of state requirements for employers with regard to income, state unemployment, and workers' compensation taxes.

If you employ your children or grandchildren, their earnings are deductible. Family businesses do not need to pay Social Security or unemployment taxes on minor children, and the children pay no income taxes on the first $3,000 of earned income. To substantiate this claim, keep time records of their work (the records will be more believable to the IRS if a non-relative keeps them), note the work done, and pay family at the rate you would pay a non-family member for the same work.

4. State and Local Taxes: Depending on where you live, you will face a variety of state and local tax requirements. All but nine states (Alaska, Wyoming, Nevada, Florida, Tennessee, South Dakota, New Hampshire, Texas, and Washington) have state personal-income taxes. But even those may have taxes on business. For example, Florida levies an income tax on corporations. Some cities, like Kansas City, have earnings taxes apart from the state income tax; others have unusual taxes on business. New York, for example, taxes unincorporated businesses.