The full picture
The Severe Mental Impairment (SMI) Disregard is a long-standing council tax rule that removes a person from the household count for council tax purposes when a doctor has certified them as severely mentally impaired. It's been in legislation since 1992 but is one of the most under-claimed council tax discounts — many families with dementia don't know it exists.
Who counts as "severely mentally impaired" for council tax purposes: - Diagnosed with a condition that severely impairs intellectual and social functioning, expected to be permanent - Common qualifying conditions: dementia (Alzheimer's, vascular, Lewy body, frontotemporal), severe learning disability, severe stroke effects, Parkinson's disease in advanced stages, Huntington's disease, severe and persistent depression with cognitive impact - Receives one of: Attendance Allowance, PIP daily living, DLA middle/highest care, ADP daily living, Constant Attendance Allowance, Severe Disablement Allowance, Incapacity Benefit, Income Support with disability premium, Universal Credit Limited Capability for Work
What the disregard means for the bill: - If the SMI person lives alone, the home is fully exempt from council tax (Class U exemption — 100% off) - If they live with one other adult, that adult gets the Single Person Discount (25% off) - If they live with two or more other adults, no discount applies but the SMI person doesn't count for council tax purposes - Backdating: many councils backdate to the date the qualifying benefit started — sometimes years of refunds
In England, Scotland and Wales the rule is the same. Northern Ireland has an equivalent under the Rates system: Disabled Persons Allowance + SMI exemption from rates.