Annexe Second Home Premium Exception: How to Avoid the 100% Council Tax Surcharge

The New Premiums and Why Annexe Owners Should Pay Attention

Since April 2025, English billing authorities can charge a 100% second home premium on furnished properties that are nobody's sole or main residence — doubling the standard council tax bill. Since April 2024, the empty home premium kicks in after just one year of a property sitting unoccupied and unfurnished, down from the previous two-year threshold.

A separately banded annexe that sits between uses — perhaps empty after a relative moved out, or furnished but not currently someone's main home — can look to the council like exactly the kind of property these premiums target. Without the right exception, the bill could jump from Band A charges of around £1,200 to £2,400.

The Class F Statutory Exception

The government anticipated this problem. The Council Tax (Prescribed Classes of Dwellings and Consequential Amendments) (England) Regulations 2024 created mandatory national exceptions under Class F (Class 3), specifically protecting integrated family annexes.

An annexe that forms part of a single property containing a main dwelling, and is being used by a resident of that main dwelling as part of their sole or main residence, is mandatorily excepted from both the long-term empty premium and the second home premium.

This is not a discretionary council decision — it is a national statutory exception that every billing authority must apply.

What "Used as Part of the Main Home" Means

The Class F exception uses the same language as the 50% family annexe reduction. The annexe must form part of the same property as the main dwelling, and a resident of the main dwelling must use it as part of their main home.

This covers spaces used as a home office, studio, gym, extra living room, or guest bedroom — any genuine extension of the main household's daily living. The space does not need to be occupied as someone's separate residence.

If a relative lives in the annexe as their sole or main residence instead, the annexe is not "used as part of the main home" — but it is occupied, so it falls outside the second home and empty home premium definitions entirely. The premiums only apply to properties that are nobody's sole or main residence.

When Premiums Can Still Apply

The premiums may bite in a few specific scenarios:

• Furnished annexe between tenants. If the annexe was commercially let and is sitting empty between lettings, it may not qualify for the Class F exception if the main-home resident is not using the space
• Annexe left empty after a bereavement. After a dependent relative dies, the annexe may sit empty while the family decides what to do. The Class F exemption under the Council Tax (Exempt Dwellings) Order can cover the period before probate and up to six months after probate. A separate Class I exception can prevent an empty-home or second-home premium for up to 12 months after probate if its conditions are met; after that, Class T or another premium exception may be relevant
• Annexe used solely for holiday letting. Commercial holiday lets are outside the scope of the family exception

How to Protect Your Annexe

If your council sends a premium demand notice for an annexe that is part of your household, respond promptly with evidence that the space is used as part of the main dwelling. Utility bills, photographs showing the space is furnished and integrated with the main house, and a written declaration of use are typically sufficient.

For empty annexes restricted by planning conditions, a Class T exemption claim removes the bill entirely — which also removes any premium.

Our Annexe Discounts and Exemptions Guide covers the full premium exception framework, including the evidence needed to establish Class F protection and the fallback options if a premium is incorrectly applied. Our sibling guides on second home premiums and empty home premiums cover the broader premium rules in detail.

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