Evidence Needed for an Annexe Council Tax Exemption or Discount

Why Evidence Matters More Than Eligibility

Many families who are legally entitled to an annexe council tax discount or exemption get refused — not because they fail the eligibility test, but because they submit incomplete or wrong evidence. Councils process applications based on what you send, and front-line staff will reject a claim that looks thin even if the underlying facts support it.

Getting the evidence right the first time avoids weeks of back-and-forth correspondence and prevents the common experience of being told "you don't qualify" when the real problem was "you didn't prove it."

Evidence for Class W Exemption (Dependent Relative)

Class W gives a 100% exemption when the annexe is the sole or main residence of a dependent relative of a person who lives in the other dwelling. The council needs evidence of three things: the family relationship, the relative's dependency status, and their residence in the annexe.

Proof of dependency (one of three routes):

Age 65+ route: Passport, birth certificate, or driving licence showing the relative's date of birth. This is the simplest — no medical evidence needed.

Severe mental impairment route: A medical certificate from a registered medical practitioner (usually the relative's GP) confirming severe mental impairment, plus a benefit award letter showing entitlement to a qualifying benefit — Attendance Allowance, PIP daily living component, the care component of DLA, or certain other qualifying benefits. Some GPs charge for the certificate; this is their choice and not set by law.

Substantial and permanent disability route: Medical evidence confirming the disability is both substantial and permanent. A PIP or Attendance Allowance award letter is the strongest supporting document, but councils also accept consultant letters, occupational therapy reports, or other specialist evidence.

Proof of family relationship: A statutory declaration, a birth or marriage certificate, or a letter confirming the relationship. The definition of "relative" is broad — it includes in-laws, step-relatives, and half-blood relationships.

Proof of residence in the annexe: Electoral register entry at the annexe address, utility bills in the relative's name, GP registration showing the annexe address, or a council tax account in their name. The council needs to see that the annexe is the relative's sole or main residence, not just a place they visit.

Evidence for Class T Exemption (Empty Annexe With Planning Restriction)

Class T gives a 100% exemption when the annexe is unoccupied and cannot be let separately because of a planning condition. The evidence is simpler but very specific:

The planning decision notice from the local planning authority, showing the condition that restricts the annexe to ancillary use only. The condition typically says something like "shall not be occupied other than for purposes ancillary to the residential use of [Main House]."

If you do not have the original notice, search the local planning authority's online planning register using your property address. The decision notice and any associated conditions are usually available as downloadable PDFs.

A Section 106 agreement is an alternative to a planning condition — it achieves the same restriction through a legal obligation rather than a condition on the permission.

The council may also conduct a physical inspection to confirm the annexe is genuinely unoccupied.

Evidence for the 50% Family Annexe Reduction

This is the lowest evidence bar of the three. The council needs:

• Proof of the family relationship between the annexe occupant and the main-home council tax payer
• A declaration confirming the annexe is either used as part of the main home or occupied by a qualifying relative

Some councils accept a signed self-declaration. Others request a utility bill, electoral register entry, or similar document showing the annexe occupant's address.

Letters of Authority for Family Helpers

If you are managing the claim on behalf of an elderly or disabled relative, the council will want to see written authorisation. A simple signed letter from the relative (or their attorney under a Lasting Power of Attorney) giving you permission to act on their behalf is usually sufficient.

Without this, the council may refuse to discuss the claim with you, even if you are the person gathering the evidence and completing the forms.

What Happens After Submission

Councils typically acknowledge receipt and process applications within 21 to 28 working days. During this period, existing council tax bills remain due. If the claim is granted, the council issues a revised demand notice and refunds or credits any overpayment.

Our Annexe Discounts and Exemptions Guide includes a detailed evidence checklist for each claim type and a printable tracker for recording what you have submitted and when.

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