Working Under the Table
I had a similar situation. My daughter's father is a waiter at a very upscale restaurant and on his income statement claimed he only made $2,000.00 a month.
I did my research. I went on the internet and located a website for the restaurant, which included its dinner menu, as this is the only meal served. I averaged the cost of an individual appetizer, entree and a non-alcholic beverage and created a conservative scenario of two dinners, sharing one appetizer, two entrees and two non-alcholic drinks.
I called the restaurant and spoke with the manager, who stated, at a minimum, a server would have, on average, four tables per hour, unless they were extremely busy.
Using the above information, I was able to show that, on a conservative average, he was making almost $38/hour in tips alone, not including minimum wage. Compared to his paystub illustrating $15/hour in tips, not including minimum wage.
I was successful, his child support was based on the average between my research and his actual paystub amount.
Do you homework based on his current trade? Call local employers, tell them you're doing a labor market survey and they will readily answer your questions. If he's in construction in a union trade, call the union for current pay scale. If you present a conservative scenario, where you appear to be fair-minded you stand a chance.
If he's simply stating he is unemployed and working under the table, you'll have to be more creative. If you know where he lives, take a field trip and see where he goes during the day...like to his undeclared job. Base your scenario on your observation.
It sounds like a lot of work, but I went from $125/month to $562/month. Did I mention, I offered to not take child support, if he would visit with her once a month? He refused, so I went the extra mile.
Hope this helped.