How do file for child support if both of your names are on a business licence?

Presuming you are separated, declare on your Financial Disclosure Form how much of the joint income actually ends up going to you; if you are still together, declare all of it, and include all expenses on the expense side as well.  The FDF does not have to be perfect, just honest.  Add sheets with notes if the reality of your situation cannot be made to be fairly reflected on the form.  You would probably benefit from a consultation with a family law specialist.