Step One: Calculate Your After_Tax Income. Your after_tax income is what remains of your paycheck after taxes are taken out, such as state tax, local tax, income tax, Medicare, and Social Security. If you're an employee with a steady paycheck, your after_tax income should be easy to figure out. Look at your paystubs. If health care, retirement contributions, or any other deductions are taken out of your paycheck, add them back in.
Begin by listing your income for the month. This should include any paychecks you receive, as well as income from other sources like child support or investments. If you have a business, you should include the amount that you pay yourself out of the business each month.