Tax evasion is the deliberate action of one party to avoid or unlawfully minimise the amount of tax they have to pay to the federal government, which includes doing so for the purpose of reducing their child support liability. So, in answer to your question, the amount of tax ultimately made for the funds is immaterial. Regardless of whether the person receiving the funds paid more tax as a result of having done so, the person who deliberately acted to evade paying tax (or in this case, being accurately assessed for child support) would still be held liable.