Lawful development certificate — proof your project is legal

A lawful development certificate (LDC) is the local planning authority's formal, legal confirmation that something is lawful — either a development you propose to carry out without planning permission, or an existing use or building that has become lawful over time. It is not planning permission, and it is not a favour the council can refuse on planning grounds. It is a decision on fact and law: either the thing is lawful or it isn't, and the certificate records the answer.

For homeowners, the LDC has gone from a niche legal document to something lenders and buyers' solicitors increasingly expect. If you relied on permitted development for an extension or loft, a certificate is how you prove — years later, to a sceptical conveyancer — that you were entitled to. This page explains the two types, what evidence each needs, what they cost, and when getting one is worth the trouble.

The two certificates: proposed vs existing

Why you'd want one

• Proving permitted development on sale. A proposed-development certificate, obtained before you build, is clean documentary proof that your extension or loft never needed planning permission — exactly what a buyer's solicitor asks for.
• Mortgage and remortgage. Lenders are increasingly unwilling to lend against work whose lawfulness can't be evidenced. A certificate removes the question.
• Regularising an existing situation. If a use or building has gone unchallenged long enough to become immune from enforcement, an existing-use certificate establishes that lawfulness formally, rather than leaving a buyer to take it on trust.
• Certainty before committing. A proposed-use certificate is also a way to settle a genuine doubt about whether your scheme is permitted development before you spend on construction.

The evidence — and where existing-use claims are won or lost

For a proposed-development (CLOPUD) application, the evidence is the drawings and a demonstration that the scheme sits within the permitted development limits. For an existing-use (CLEUD) application — especially one relying on the passage of time to claim immunity from enforcement — the burden is on you, and it is decided on the balance of probabilities. Your evidence does the work: statutory declarations, dated photographs, utility and council-tax records, tenancy agreements, sworn statements from neighbours or tradespeople. If your evidence is precise and uncontradicted, the council should grant it; if it's vague, they can refuse.

Cost and timescale

The fee structure is rule-based rather than a flat price. For a proposed-development certificate the fee is half the fee that would be payable for the equivalent planning application; for an existing-development certificate it is the same as the full application fee. As at 2026, with the householder application fee at £548 (from 1 April 2026), that puts a householder-scale proposed certificate at £274 and an existing one at £548 (a £309 fee applies in the specific case of certifying that an existing use is lawful despite not complying with a condition). Planning fees in England re-index every 1 April, so confirm the current figure on the Planning Portal fee calculator before you apply. The determination target is eight weeks, like a planning application.

When it's worth it

A proposed-development certificate is cheap insurance on any project you're building on permitted-development rights — particularly a loft, a rear extension or an outbuilding you'll one day need to evidence on sale. An existing-use certificate is the right tool when you've bought a property with undocumented work, or want to formalise a long-standing situation before selling. Where the lawfulness is genuinely arguable, it's a question for a professional before you apply, because a refusal is a matter of public record.

How this connects to your Planning Permission Checker report

Your Planning Permission Checker area report establishes the designations that decide whether your project is permitted development in the first place — the conservation area and Article 4 checks that an LDC turns on. It does not prepare the certificate. A CLOPUD or CLEUD is an application to the council, made with drawings and evidence, so enquiries route to Hampstead Architecture and Planning, ARB-registered architects whose published work includes lawful development certificates.