No, I would argue that this is impermissible. The guidelines define gross income as:
“(1) Gross Income. “Income” means a parent’s actual gross income from any source, including but not limited to income from employment or self-employment (salaries, wages, commissions, bonuses, dividends, severance pay, etc.), ownership or operation of a business, partnership, or corporation, rental of property, retirement or pensions, interest, trusts, annuities, capital gains, social security benefits, workers compensation benefits, unemployment insurance benefits, disability pay and insurance benefits, gifts, prizes and alimony or maintenance received from persons other than the parties to the instant action.”
If you deduct taxes from gross income, it is essentially not gross income. Nothing should be subtracted from a parent’s gross income.