Also known as "divided custody" although the latter concept is mostly used to describe split custody over greater periods of time such as alternate years with each parent.
In Canada, the Child Support Guidelines have adopted this term to refer specifically, and to thereafter impose a child support formula unique to the arangement, as follows:
"8. Where each spouse has custody of one or more children, the amount of a child support order is the difference between the amount that each spouse would otherwise pay if a child support order were sought against each of the spouses."