Download the Form SE 1040 from the Internal Revenue Service (IRS) website. Print a copy and complete the required sections. Print a copy of the instructions for the form as well (See References).
Read page one and follow the directions to determine which form to use. It will be the Short Schedule or the Long Schedule, depending on your situation.
Add all earnings from your self-employment ventures. This may be farming, as shown on your Schedule F. Enter the total on the appropriate Line 1. Also include any Social Security benefits on the following line.
Place net earnings or losses shown on your Schedule C if you have on Line 2. Add lines 1 through 2 together and place the total on Line 3.
Multiply the total on Line 3 by .9235. This is the number that goes in Line 4 showing your net earnings from self-employment.
Follow the instructions on Line 5 and multiply the number on Line 4 by the corresponding amount. For instance, earnings of $106,800 or less are multiplied by .153.
Multiply Line 5 by .50 to get the deductions amount on Line 6. This is equal to one-half of your self-employment tax.