6 February 2026
Planning Alert: Avoiding 'Life-Changing' CIL Charges on Your Extension
A recent council review highlights the financial risks of CIL errors for homeowners planning residential extensions.
A local authority has recently voted to conduct an independent review of its Community Infrastructure Levy (CIL) practices following reports of homeowners being hit with 'life-changing' financial charges. The review was triggered after several residents, who were undertaking home improvements and self-build projects, found themselves liable for tens of thousands of pounds in fees due to minor administrative errors. At the heart of the issue is the 'Commencement Notice'—a mandatory document that must be submitted to the council before any physical work begins on-site. Failure to submit this form on time, or at all, can result in the immediate loss of 'Self-Build Exemptions,' even if the homeowner was otherwise entitled to them. This creates a scenario where a project intended to be levy-free suddenly incurs a massive debt, often with additional surcharges and interest, leaving homeowners in significant financial distress. The investigation will now examine whether the council’s communication and enforcement of these rules have been sufficiently transparent.
For London homeowners, this news serves as a critical warning. The Community Infrastructure Levy (CIL) is a charge that most London boroughs apply to new developments—including residential extensions over 100 square metres—to help fund local infrastructure like schools and transport. While many extension projects qualify for a 'Self-Build' exemption, meaning you don't have to pay the levy, the process is notoriously bureaucratic. As seen in this recent case, the planning system is often unforgiving. In London, where CIL rates can be particularly high depending on the borough, an administrative oversight can easily add £20,000 to £50,000 to your build cost overnight.
At London Extend, we frequently see how complex the CIL landscape is for the average homeowner. Each borough, from Wandsworth to Barnet, has its own charging schedule and specific requirements. The most common 'trap' is the timing of paperwork. Homeowners often assume that receiving planning permission is the final hurdle, but the CIL process continues right up until the day the shovel hits the ground. If you start work—even just minor site preparation—before the council has acknowledged your Commencement Notice, you legally forfeit your right to an exemption. There is currently very little room for appeal once this mistake is made, which is why the 'life-changing' nature of these charges is no exaggeration.
This story highlights why professional management of the planning process is essential. It isn’t just about getting a 'Yes' from the council; it is about navigating the post-approval obligations that protect your budget. Homeowners must ensure they have a 'Liability Notice' and an 'Exemption Confirmation' in writing before proceeding. If you are planning a significant extension or a basement conversion in London, you must treat CIL paperwork with the same level of importance as your structural drawings.
We advise all our clients to never assume their builder or architect has 'sorted' the CIL unless it is explicitly confirmed in writing. The liability always rests with the landowner. This recent move toward an independent review suggests that the pressure is mounting on councils to be fairer, but until the national legislation changes, the burden of compliance remains with you. By working with experts who understand the granular details of London planning law, you can ensure your dream home improvement doesn't turn into a financial nightmare.