On schedule C I can not get passed or override the question Principal Business Code. I do not know where to find it. I called my paying company and they do not know.
Here is the link for the Schedule C instructions. We can't look it up for you but the principal business codes are listed on pages 16-17: http://www.irs.gov/pub/irs-pdf/i1040sc.pdf
Note that if your business can’t be classified, enter 999999 as the principal business code.
Hope that helps!