Enter income from various self employed sources on lines 1 thru 3. Add these lines and multipy by 92.35%. (This deducts employer FICA tax from your income.) Line 5 - You pay 15.3% on the first $106,300 and 2.9% on amounts above that. Put this total on your 1040. Line 6 - Deduct 1/2 of line 5 from AGI.