I know that, as an independent contractor, my boss withholds NOTHING from my check. I also know that I have to pay quarterly estimated income tax, and will do that. But - my question is - what about FICA taxes? Do I have to pay those also? How? Thanks! *** email edited

FICA taxes are paid/calculated on Form 1040 Schedule C (Profit or Loss from Business). Businesses are required to withhold FICA (and medicare) taxes from their employees' income. They match that amount when they pay it to the feds. On Schedule C, they will calculate both amounts (I don't think it's quite twice as much) and you pay it then. You have to include this in your quarterly estimated tax payments.

You will report your income and expenses on schedule C or C-EZ (Form 1040). This income is subject to SE tax at 15.3%. You will pay estimated taxes if required. Read: Your U.S. Tax Return: Tax Filing by Self Employed Sole Proprietor or Independent Contractor