Apportionment of housing costs: exempt income
17. For the purposes of calculating or estimating exempt income the amount of the housing costs of a parent shall be—
(a)where the parent does not have a partner, the whole amount of the housing costs;
(b)where the parent has a partner, the proportion of the amount of the housing costs calculated by multiplying those costs by—
where—
A is the number of relevant children (if any);
B is the number of children in that parent’s family (if any);
(c)where the parent is a member of a polygamous marriage the proportion of the amount of the housing costs calculated by multiplying those costs by—
where—
A and B have the same meanings as in sub-paragraph (b); and
X is the number which is one less than the number of partners.