I'm a single mom raising my daughter and was initially doing pretty good financially (keeping 2 jobs). I am presently working about 20-25 hours weekly with one job of which I've been employed ten years now. My ex husband has his own business, but whenever we go to court he somehow manages to produce tax papers showing he makes the same as I do $40,000 annually. I'm struggling to pay a car note of $350 monthly while he is driving a brand new Range Rover 2015 and renting a house that's about $1500 monthly (guessing on his rent). How do I obtain his true pay legally. He has his own limo business which he advertises on the Internet. Please help??

Hiring a lawyer might be able to help determine whether or not he is printing out bogus tax forms, but that's about it.
A more likely possibility is that he is making up deductions and/or not reporting some of his cash income. That means that even if he is showing the court real copies of his tax forms, he could be padding expenses/hiding income to the IRS. And that will be extremely difficult if not impossible to determine (unless the IRS does an audit and makes him produce all his proof of business expense, and even scrutinizes how he manages to pay for things).

In today's environment, I can actually see an internet limo business costing more and making less than you think. But it's also common for small, one person businesses to cheat on their taxes.

40-50 years ago I would hear stories of people getting the IRS to audit someone. I'm not so sure they respond to suspicious exes anymore.
You could try. You can call around to several lawyers to see what they would charge and if they think it's worth it.
I don't think it is. This is a job for the IRS.

Something I don't understand about your post - you are divorced, and so at the time of your divorce there must have been an agreement or court order regarding alimony and/or child support amounts. What difference does it make now after the divorce whether his income goes up, down, or sideways?

But to answer your question - if he has shown his tax filings in court then you have about as much info as you can hope for. I would second Joy's statement that as owner of a company he is probably writing off substantial business expenses, including perhaps his car.

What you need to do is an accounting of the business. Also you need to compare it to other businesses of similar size. That way no matter what the returns say the judge could impune an amount that differs from the actual return.

I guess I will ask, when he is questioned in court by your attorney, as to how he pays for the house, how he pays for the car, how he maintains his life style, what budget does he produce to prove he lives on this income ?