“ To do this, file a new Form W-4, Employee’s Withholding Allowance Certificate, with your employer. "Does this not apply to me?”---->You can change the number of withholding allowances on your W4 as an employee as many times as you want, but you are a part time IC that needs to file FORM W9, not Form W4. So, as a part time IC, a self-employed individual,as said previously, you would report your income and expenses using either Sch C or Sch C-EZ. In addition you may be required to file Schedule SE, Form 1040, Self-Employment Tax and you may also need to pay quarterly estimated taxes. For instance, you, also as an employee, receive wages, and your wages received can reduce the amount of self employment income that is taxed for OASDI as long as your wages + self-employment income > $106,800 for 2010. For example, assume that you receive wages amounting $83,300 and your net earnings from self employment amount to $24,600. Then you must count $23,500 of your earnings in determining taxable self-employment income for OASDI taxes. I mean $106,800( FICA Tax base)-Wages received $83,300=$23,500( Your taxable self-employment income).