The overriding goal of the Court is to find income available for support. This means that there are business deductions that the IRS allows, but which are not deductible for support purposes.
Depreciation is an allowable business deduction on your tax returns, but for support purposes, this deduction is almost always added back to income, because it is a fictional expense that does not require the business owner to actually pay for it. By adding back the depreciation deduction, the amount of cash flow available for support increases. This, of course, will increase the amount of the support obligation.
If you are a corporate entity such as an LLC, you may have large retained earnings noted on your tax returns. These retained earnings are often challenged in court, because allowing the corporation to keep these funds on hand, reduces the amount of income or cash flow available for support.