Severe Mental Impairment Council Tax Exemption in Hillingdon

What the SMI Disregard Does

Severe Mental Impairment (SMI) is a specific council tax status — not a general disability classification. A person with SMI is "disregarded" for council tax purposes, meaning they're treated as if they don't live in the property for the purposes of working out how many adults are resident.

The practical effects depend on who else lives in the home:

• Person with SMI lives alone: the property is 100% exempt from council tax. No bill at all.
• Person with SMI lives with one other adult: the other adult qualifies for the 25% Single Person Discount, because the SMI person doesn't count.
• Person with SMI lives with multiple adults: the SMI person is disregarded from the count, which may trigger or increase discount entitlement.
• All residents have SMI: the property is fully exempt.

This is separate from Council Tax Reduction. SMI is a statutory disregard applied to the bill before any CTR calculation takes place. The two can work together — an SMI discount reduces the bill, and then CTR reduces whatever remains.

Who Qualifies

Two conditions must both be met:

1. Medical certification: A registered medical practitioner (GP or consultant) must certify that the person has a severe impairment of intelligence and social functioning which appears to be permanent. This is a specific clinical determination — a diagnosis of dementia, severe brain injury, severe learning disability or another condition causing permanent cognitive impairment.

2. Qualifying benefit: The person with SMI must also be entitled to at least one qualifying benefit:

• Attendance Allowance
• PIP Daily Living Component (either rate)
• DLA Care Component (middle or higher rate)
• Disability Working Allowance or Working Tax Credit disability element
• Incapacity Benefit
• Employment and Support Allowance
• Severe Disablement Allowance
• Universal Credit (with the Limited Capability for Work element)
• Armed Forces Independence Payment
• Constant Attendance Allowance

The benefit confirms that the person's impairment has been formally recognised in the welfare system. Without both the medical certificate and the qualifying benefit, the SMI disregard can't be applied.

How to Apply

Contact Hillingdon Council's council tax team and request an SMI disregard application. You'll need to provide:

• A completed SMI declaration form (the council supplies this)
• A medical certificate from the person's GP or consultant confirming severe mental impairment
• Evidence of the qualifying benefit (award letter)

If the person can't manage the application themselves, a family member, carer or someone with power of attorney can apply on their behalf.

You can ask Hillingdon to apply the disregard from the date the person first met both conditions (medical certification and entitlement to a qualifying benefit). If the council accepts that date, it can reduce past bills. A fully exempt property on a Band D rate in Hillingdon saves £2,045.46 per year.

SMI Plus Council Tax Reduction

If the SMI disregard reduces the bill but doesn't eliminate it entirely (because another liable adult lives in the property), that remaining liability can then be assessed for Council Tax Reduction under Hillingdon's working-age or pensioner scheme. The SMI disregard affects the adult count for council tax discounts; CTR income is assessed separately under the applicable Hillingdon scheme.

For the full range of council tax discounts and the CTR application process in Hillingdon, see our Hillingdon Council Tax Reduction guide.

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