The basic principles
5 Child support maintenance: supplemental provisions.
(1)
Where—
(a)
there is more than one person with care of a qualifying child; and
(b)
one or more, but not all, of them have parental responsibility for F1... the child;
(2)
Where more than one application for a F2maintenance calculation is made with respect to the child concerned, only one of them may be proceeded with.
(3)
The Secretary of State may by regulations make provision as to which of two or more applications for a F2maintenance calculation with respect to the same child is to be proceeded with.