Council Tax Reduction pays two families when the oldest adults tie, and picks the claimant by age rather than liability #2135

benunit_contains_household_head is benunit_max_age == household_max_age. When the oldest adults of two benefit units in one household are the same age, both units are flagged, and every Council Tax Reduction scheme pays each of them a full award.

Reproduction on main (ae980d1e3, 2026): two single adults of the same age in separate benefit units of one household, council tax £1,800, no income, claims_all_entitled_benefits: true.

The age rule is also wrong without a tie. Only a person liable to pay the council tax is in a class entitled to a reduction (for example SI 2012/2885 Sch 1 para 2(a), SSI 2021/249 reg 13), and liability follows the resident's interest in the dwelling (LGFA 1992 s.6, s.75), not age. So a pensioner living in their adult child's home is treated as the claimant, and the household is put on the pensioner scheme.

Fixed by #2009.