Untaxed income

How should untaxed income be handled when entering amounts into your or the states child support calculator since the amounts normally entered are gross pay? My wifes lawyer said to multiply the amount paid by 20% then add this to the amount calculated using your gross income. Is this correct?

I’m not sure I understand; gross income is income before taxes are removed. So untaxed income is treated the same was as gross (pretax) income on the child support worksheet.