To be able to qualify for the severe disability premium (SDP):
the disabled person must receive a qualifying disability benefit: disability living allowance care component at the middle or highest rate, or attendance allowance (or constant attendance allowance), or the daily living component of personal independance payment; and
no one gets carer’s allowance for looking after them (Carer’s Allowance can be claimed by those who look after those receiving a qualifying disability benefit, and meet certain other conditions); and
they either live alone or are treated as living alone (or are a couple where both receive a qualifying benefit).