CIL Self-Build Exemption: How to Claim It for Your North London Project

Introduction

Community Infrastructure Levy (CIL) is a charge payable to the local planning authority on new floor area created by development, with rates varying significantly between boroughs — in Camden, up to £350/sqm; in Islington, £261/sqm; in Barnet, £95/sqm. For homeowners building an extension or carrying out other development that creates new floor area, CIL can be a significant additional cost. However, the CIL Regulations provide an exemption for self-build projects — where the homeowner is building or extending their own principal home. This guide explains who qualifies for the self-build exemption, how to claim it, and the critical procedural requirements that must be met to avoid paying the levy or triggering a clawback.

Who Qualifies for the Self-Build Exemption?

The CIL Regulations 2010 (as amended) provide for several residential exemptions, the most commonly applicable of which are:

Self-Build Housing Exemption (Regulation 54A)

A person who builds their own home — creating a whole new dwelling — is exempt from CIL on the floor area of that dwelling. The exemption applies where:

• The person builds or commissions the construction of their own principal residence (must occupy it as their principal home)
• The person occupies the property as their principal home for a period of at least 3 years after completion

Residential Annex Exemption (Regulation 42A)

A homeowner extending their existing property to create a single self-contained residential annex within the curtilage of their home is exempt from CIL on the annex floor area.

Extensions to Existing Dwellings (Regulation 42)

An extension to an existing dwelling by the owner of that dwelling — adding floor area to an existing house — is exempt from CIL. This is the most commonly applicable exemption for north London homeowners carrying out rear extensions, loft conversions, or other works that create additional floor area in their home. Key requirements:

• The owner must occupy the property as their principal residence
• The works must not result in the creation of a new dwelling or a self-contained unit
• The exemption must be claimed before development commences

How to Claim the Exemption

The CIL self-build and extension exemptions are not automatic — they must be claimed by submitting the appropriate form to the local planning authority before development commences. The process is:

1. Submit CIL Form 7 (Self-Build Exemption Claim — Residential Extension): This form is submitted to the LPA to claim the Regulation 42 extension exemption. It must be submitted and the exemption confirmed by the LPA before any work begins on site. Starting work before the exemption is confirmed means the exemption is lost.
2. Receive confirmation from the LPA: The LPA will review the claim and confirm whether it accepts that the proposed works qualify for the exemption. This is typically a straightforward administrative process for a homeowner extension.
3. Commencement Notice: When works begin, a Commencement Notice (CIL Form 6) must be submitted to the LPA on the day works commence or before. Again, failure to submit before commencement means the exemption is lost and CIL becomes due at the full rate.

Critical Procedural Requirements — Do Not Miss These

The most common reason homeowners lose their CIL exemption is failure to follow the procedural requirements:

• Claim the exemption before starting work: If work begins before Form 7 is submitted and accepted, the exemption is automatically lost. This is not discretionary — there is no mechanism to reinstate the exemption retroactively.
• Submit a Commencement Notice before breaking ground: Even after the exemption is confirmed, failing to submit Form 6 before commencement triggers the loss of exemption. The commencement notice must be submitted on the day works commence or before.
• Occupy for 3 years (Self-Build): For the self-build housing exemption (not the extension exemption), the homeowner must occupy the property as their principal home for a minimum of 3 years after completion. If the property is sold within 3 years, CIL becomes payable on the chargeable amount (clawback).

Mayoral CIL

In addition to the borough CIL, the Mayor of London's CIL 2 charge (£60/sqm for all new residential floor area in London) applies. The Mayoral CIL is administered and collected by the borough on behalf of the GLA. The self-build extension exemption from Regulation 42 also exempts the Mayoral CIL for the same works. A separate Mayoral CIL exemption claim is not required — the borough's Form 7 claim covers both borough and Mayoral CIL.

CIL and Permitted Development Works

Works carried out under permitted development rights — without a formal planning application — are not subject to CIL. CIL only applies where planning permission is granted (including prior approval under PD). For works that are genuinely within PD, no CIL is payable and no exemption claim is needed. Where a lawful development certificate is obtained for PD works, the works are still not subject to CIL.

Conclusion

The CIL self-build exemption for residential extensions provides significant financial relief for north London homeowners — potentially saving tens of thousands of pounds in CIL charges in high-rate boroughs like Camden and Islington. The critical requirement is procedural compliance — the exemption must be claimed before work starts, and a Commencement Notice must be filed before any work is done. An architect managing a planning application in a CIL-charging borough will advise on the exemption, prepare and submit the required CIL forms as part of the planning process, and ensure that the Commencement Notice procedure is followed correctly when construction begins.