In Maltese v. Choghri, the court states that self-employed payors have an inherent obligation to put forward comprehensive records of income and expenses to establish their income. A self-employed person has the onus of clearly demonstrating the basis of his or her net income by demonstrating that deductions from gross income should be taken into account in the calculation of income for support purposes.
http://www.canlii.org/en/on/oncj/doc/2016/2016oncj48/2016oncj48.html