Make child support a tax deduction for the person paying, and require the recipient to claim it as income.

While it is understood that a custodial parent should receive
support from the non-custodial parent, that support should be treated fairly. The non-custodial parents should be able to claim a credit or deduction on their tax returns each year and the custodial parents should be required to claim the support as income.
This will perhaps encourage non-custodial parents to make their payments in a more timely manner and possibly reduce the amount of false claims made each year.