Your extension qualifies as permitted development. Your builder is ready. You could start work tomorrow. But should you? Without a piece of paper confirming the work is lawful, you're relying entirely on your own interpretation of the rules - and if you've got it wrong, or if the rules change, or if someone challenges the work, you have no formal protection.
A Lawful Development Certificate (LDC) is that piece of paper. It's a formal confirmation from your local council that your proposed work is lawful and does not require planning permission. It costs £274, takes around 8 weeks, and it could save you thousands when you sell.
When you sell your home, the buyer's solicitor will check the planning history. Every extension, loft conversion, and outbuilding needs to be accounted for. If the work had planning permission, there's a record. If it was permitted development with an LDC, there's a record. If it was permitted development without an LDC, there's nothing - and that's where problems start.
Without documentation, the buyer's solicitor may require you to apply for a retrospective LDC or take out indemnity insurance before the sale can proceed. This causes delays, costs money, and in some cases makes buyers walk away entirely. An LDC applied for before you start work eliminates this risk completely.
£274 now or a delayed sale later. An LDC is the cheapest insurance you'll buy.
A Certificate of Lawfulness of Proposed Use or Development (CLOPUD) is applied for before work starts. It confirms that the proposed development is lawful and doesn't need planning permission. This is the one most homeowners should use. The fee is £274 as of April 2026.
A Certificate of Lawfulness of Existing Use or Development (CLEUD) is applied for after work has been done. It confirms that existing development is lawful - either because it was permitted development at the time, or because it has been in place long enough to be immune from enforcement (the 10-year rule). The fee is also £274. You'll need to provide evidence that the work meets PD conditions or has existed for the required period.
This is the key distinction. A planning application is assessed against planning policy - the council exercises discretion and can refuse it even if it technically meets the rules, based on design quality, neighbour impact, or local policy. An LDC is assessed purely on the facts. The council checks whether the proposed work meets the PD conditions. If it does, they must grant the certificate. There is no discretion, no design review, and no neighbour consultation.
This means an LDC cannot be refused on the basis that a neighbour objects, that the design isn't attractive, or that the council doesn't like extensions in your street. If the measurements, heights, positions, and materials meet the GPDO conditions, the certificate is granted. If they don't, it's refused - and you know you need to apply for planning permission instead.
Want to check whether your project qualifies for PD before applying for an LDC? A free eligibility check takes about two minutes.
Unlike planning permission, which gives you 3 years to start work, an LDC confirms lawfulness on the date it is issued. If the GPDO rules change between the date of your certificate and the date you complete the work, the certificate may no longer be valid. In practice, this is rare - the GPDO doesn't change often - but it means you should start work reasonably promptly once you have the certificate.
If you're concerned about potential changes (for example, if a new Statutory Instrument has been announced), apply for the LDC early and begin work as soon as it's granted.
An LDC is recommended but not legally required. If your project clearly falls within PD rules - a small rear extension on a house with no conservation area designation, no Article 4 direction, and no previous extensions - the risk of a problem is low. Many homeowners proceed without one.
But if any of the following apply, an LDC becomes much more important: you're near the limits of PD (close to the maximum depth, height, or curtilage), you're in or near a conservation area, the property has been extended before, the work is substantial enough to affect resale value, or you plan to sell within the next few years.
Common mistakes that cost money
Applying for planning permission when an LDC would do. If your project is PD, an LDC is cheaper (£274 vs £548), faster, and cannot be refused on design or policy grounds. Only apply for planning permission if the work genuinely needs it.
Not applying for anything at all. The work might be perfectly lawful - but without a certificate, you have no proof. When you sell, this becomes your problem.
Confusing an LDC with planning permission. An LDC is not permission to build. It's confirmation that you don't need permission. The distinction matters legally and when communicating with solicitors during a sale.
PD Assessment Tool
Before spending £274 on an LDC application, it's worth confirming your project qualifies for permitted development. Our free eligibility check covers property type, designated area status, and the key conditions for your project type. If you pass, the full assessment produces a formal document that maps every PD condition - giving you confidence before you submit.
Free eligibility check. Full assessment £47.
Content verified against the Town and Country Planning Act 1990, sections 191 (CLEUD) and 192 (CLOPUD), and GOV.UK guidance on lawful development certificates. Fee figures verified against MHCLG published schedule effective 1 April 2026. This page is for general information only and does not constitute legal advice.
April 2026