In England, an owner may be able to claim an exemption from the Community Infrastructure Levy (CIL) for a qualifying residential annexe built within the grounds of their home. The exemption has advance application steps and later-use conditions. It does not itself grant planning permission or establish that an annexe can be occupied or transferred separately.

Check the exemption conditions before work starts

CIL applies only where the relevant charging authority has adopted and published a charging schedule. For the residential-annexe exemption, the main dwelling must be the claimant’s principal residence, and the claimant must have a material interest in it. The annexe must be wholly within the main dwelling’s curtilage and comprise one new dwelling. Government guidance does not require the annexe’s occupier to be related to the main-home owner or to stay for a specified period.

The claim must be submitted to the collecting authority before development commences, using the residential-annex claim form. The authority must grant and notify the exemption before the chargeable development begins; the claim lapses if work starts before the decision notice. A commencement notice must also be received before work begins. Check the current form, local authority instructions, and the project’s CIL liability before site work starts.

Track the three-year clawback period

The three-year period starts on the date the relevant compliance certificate for the annexe is issued. Under the current guidance, the exemption is withdrawn if any of these events happens during that period:

  • the main home is used for a purpose other than as a single dwelling;
  • the annexe is let; or
  • the main home and annexe are sold separately from one another.

For this purpose, completion is tied to the relevant building-regulations or Building Act compliance certificate. If a disqualifying event occurs, the person who received the exemption must notify the charging authority in writing within 14 days. The authority will withdraw the exemption and the CIL that would have been due when the claim was made, or the lower amount of relief granted, may become payable.

Keep the exemption decision, commencement notice, completion certificate, and any correspondence with the authority together. Before letting or agreeing a separate transfer, check the certificate date, the original claim, and the authority’s current requirements. A CIL exemption does not override a planning condition, title restriction, tenancy rule, or other approval requirement.

Distinguish current rules from proposed changes

On June 25, 2026, the Government wrote to CIL charging authorities about household exemptions. The letter restated that applicants must receive confirmation of an exemption before development commences and said the Government intended to consult on targeted regulatory changes. The letter describes proposals; it does not itself amend the CIL Regulations. Check current legislation and the collecting authority before relying on a later policy announcement or a past claim.

This guide covers the England residential-annexe CIL exemption only. CIL applies in charging-authority areas with an adopted schedule, and the result depends on the current regulations, claim record, dates, and property facts.