If the income of an obligor is not withheld as of the effective date of the support order, pursuant to subdivision (1) or (2) of this subsection, or otherwise, such obligor's income shall become subject to withholding pursuant to this section, without further exception, on the date on which the obligor becomes delinquent in maintenance or child support payments in an amount equal to one month's total support obligation.
§ 454.505, RSMo