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CIL Annexe Exemption: Residential Annexes Explained
The CIL annexe exemption can remove the Community Infrastructure Levy charge from a qualifying residential annexe built within the curtilage of your main home. It is not automatic, and the paperwork must be completed before development starts.
This exemption has its own rules. It is different from the whole-house self-build exemption and from the residential extension exemption, and it carries a specific three-year clawback period after completion.
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Who can claim the CIL annexe exemption?
The exemption is governed principally by regulations 42A to 42C of the Community Infrastructure Levy Regulations 2010.
The claimant must own a material interest in the main dwelling and occupy that main dwelling as their sole or main residence. A material interest is normally a freehold interest or a qualifying long lease under the CIL Regulations.
The proposed annexe must also:
- be wholly within the curtilage of the main dwelling
- comprise one new dwelling
Those requirements are cumulative. Meeting one does not cure a failure of the other.
The annexe occupier does not have to be a relative
There is no CIL rule requiring the person living in the annexe to be related to the owner of the main house. Nor does the annexe occupier have to promise to remain there for a set period.
That is useful because planning discussions about a granny annexe often focus heavily on who will live there. For CIL, the statutory exemption instead focuses on the claimant’s interest and main residence, the curtilage, the creation of one new dwelling and what happens during the clawback period.
The planning question is separate. A residential annexe may still need planning permission or may raise questions about whether it has become an independent dwelling. See our granny annexe planning guide.
What does wholly within the curtilage mean?
For the CIL annexe exemption, the new dwelling must be wholly within the curtilage of the main dwelling. Curtilage is not simply the same thing as ownership, the red line around a planning application or the whole garden holding.
Whether land or a building is within the curtilage is a matter of fact and degree. The Valuation Office Agency’s CIL manual explains that the annexe should be geographically close to the main house and form an integral part of it, although the degree of proximity required will depend on the facts.
This matters because regulation 116A provides a specific appeal where the collecting authority decides that the annexe is not wholly within the curtilage. The VOA cannot use that appeal to decide every other eligibility issue.
Claim the exemption before you start
The claim must be made before the chargeable development commences and the collecting authority must notify you of the exemption granted. The current claim form is Form 8: Residential Annex Exemption Claim.
Do not start excavation, demolition or other material operations simply because the form has been sent. Make sure the exemption has actually been granted before commencement.
Where liability has not already been dealt with, the wider CIL process should also be completed, including the appropriate assumption of liability. Our CIL process guide and CIL forms guide set out the sequence.
A residential annexe also needs a Commencement Notice
Unlike a qualifying residential extension exemption, an annexe exemption does not remove the Commencement Notice requirement. A valid Form 6 must reach the collecting authority before work starts.
For Liability Notices or revised Liability Notices within the post-1st September 2019 regime, if the annexe exemption has already been granted and the development starts before a valid Commencement Notice is received, regulation 83(1A) requires a CIL surcharge equal to 20% of the notional chargeable amount, capped at £2,500, rather than automatic loss of the exemption. The authority need not impose it where the surcharge would be less than its reasonable administrative costs. Starting before the exemption itself has been granted is different and can prevent the exemption being obtained.
See our main CIL process and CIL appeals guides if a notice has already been missed.
The three-year annexe clawback period
The residential annexe exemption has a three-year clawback period beginning from completion. Government guidance uses the date of the relevant Building Regulations compliance certificate to identify completion for this purpose.
Within that three-year period, the exemption can be withdrawn if a disqualifying event occurs. The current rules identify these events:
- the main house is used for a purpose other than as a single dwelling
- the annexe is let
- the main residence or the annexe is sold separately from the other
If a disqualifying event happens, the person benefitting from the exemption must notify the charging authority in writing within 14 days. The exemption can then be withdrawn and the CIL which would otherwise have been payable can become due.
Can the annexe be occupied by somebody else?
Yes. The regulations do not require the annexe occupier to be the claimant or a relative of the claimant. What matters is that the claimant continues to satisfy the main-dwelling requirement and that no disqualifying event occurs during the clawback period.
Occupation by another person is therefore not automatically the same thing as letting. But a tenancy, rent or other arrangement that amounts to letting the annexe can trigger clawback within the three-year period, so the legal arrangement matters rather than simply who sleeps there.
What if the annexe is sold or the main house is sold?
The key CIL problem is a separate sale. If the annexe is sold separately from the main residence, or the main residence is sold separately from the annexe, within the clawback period, the exemption can be withdrawn.
A sale of the whole property together is different from selling one separately from the other for the specific annexe clawback rule. However, the CIL paperwork and any local land charge should still be checked as part of the conveyancing process.
Appealing a refusal on the curtilage point
Regulation 116A gives a narrow Valuation Office Agency appeal where the collecting authority has decided that the annexe is not wholly within the curtilage of the main dwelling.
The appeal must normally be made within 28 days of the collecting authority’s decision on the exemption claim and before development commences. The appointed person can consider the curtilage issue, but cannot use regulation 116A to decide other questions such as whether the claimant occupies the main dwelling as their sole residence or whether the development comprises one new dwelling.
That narrow jurisdiction is important. If the authority refuses the exemption for some other reason, do not assume that regulation 116A provides a general appeal against the refusal. Our CIL appeals page explains the available routes and deadlines.
Retrospective permission can destroy the exemption
Government guidance now makes clear that development consented retrospectively under section 73A cannot obtain the residential annexe exemption, other than any separate minor-development exemption which may apply. A previous exemption is not simply carried over to a later section 73A permission.
This can become important where an annexe is built differently from the approved scheme and the breach is serious enough to require retrospective permission. Before applying retrospectively, check what that would do to the CIL position as well as the planning position.
Costs and planning permission for an annexe
The CIL annexe exemption is separate from the planning application itself. Whether an annexe needs planning permission depends on what is proposed and how it will be used. Our granny annexe planning guide explains that side of the project.
If a planning application is needed, the application fee is separate from CIL. See our planning application fees page.
If the underlying planning application is refused, that refusal can usually be challenged through the normal planning appeal route.
Relevant CIL rules and guidance
Community Infrastructure Levy (CIL)
CIL essentials
CIL Annexe Exemption Page Created: 30th August 2026