no it is not double taxation since the SE tax is separate and apart from income tax. if you had $100,000 in wages 7.65 % would be taken from that for Social Security and Medicare taxes which is somewhat the same as your SE Tax, There are differences. If you get a w-2 your employer would pay the other 7.65 % for Social Security and Medicare taxes on the wages. As self-employed you get to deduct 1/2 your self-employment taxes in arriving at taxable income. With a w-2 there is no similar deduction.
