Lawful development certificates: proving you never needed permission
If your extension is permitted development, you don't need permission — and you also have nothing on paper that says so. A lawful development certificate is that piece of paper. It is optional, and it is usually worth getting.
The problem it solves
Permitted development is a right, not a decision. Nobody signs anything. You measure the limits, you satisfy yourself you're inside them, you build. Which is fine, right up until somebody asks you to prove it.
That somebody is usually a buyer's conveyancer, four years later, working through the enquiries on your sale. They'll ask what authorised the extension. “It was permitted development” is an assertion. A certificate is evidence, and it moves the conversation on in about a minute rather than a fortnight.
The council can also ask. If a neighbour complains and an enforcement officer turns up, the burden of showing the work was lawful sits with you.
Two kinds, and the one you probably want
There are two, and they're often confused. A certificate of proposed use or development, under section 192 of the Town and Country Planning Act 1990, is applied for before you build. A certificate of existing use or development, section 191, is for work already done.
The proposed one is the useful one. You apply with your drawings, the council checks them against the permitted development limits, and you find out whether your reading of the rules matches theirs before you've spent anything. If it doesn't, you've learned that for the cost of a half-price application rather than the cost of a demolition.
The existing-development version is a retrospective fix. It works, but it's the more anxious route.
What it costs and how long it takes
The fee for a proposed-development certificate is half the fee for the equivalent householder planning application. Fees are set nationally and revised periodically, so use the Planning Portal's fee calculator for the current figure rather than a number you read somewhere.
Determination target is eight weeks, the same as a householder application, though straightforward ones often come back sooner. You'll need a location plan, a site plan and drawings of the existing and proposed house — the same drawing set a planning application would need, which is one reason to sort your drawings out early either way.
A council can only refuse on the facts: either the description of what you propose is lawful or it isn't. They can't refuse a certificate because they'd rather you didn't build it. That's the difference between a certificate and a planning application, and it's the reason the process is usually undramatic.
When to skip it
If you're building a modest rear extension well inside the limits, on a house with no previous extensions, on a plot that isn't designated land, and you have no plans to move — you can reasonably decide the certificate isn't worth the fee. Plenty of people do.
The calculation changes the moment any of those is untrue. Building near the edge of a limit, on a house somebody has already extended, or where the “original house” boundary is genuinely arguable, is exactly where an eight-week check beforehand is cheap insurance. So is building anywhere you might sell within a few years.
About a third of the people who come to us haven't made a planning application and don't intend to, and another fifth aren't sure whether they need one at all. For that second group, a proposed-development certificate answers the question definitively and costs less than being wrong.
Frequently asked
Where the rules come from
Sections 191 and 192 of the Town and Country Planning Act 1990 create the two certificates; the application procedure sits in the Town and Country Planning (Development Management Procedure) (England) Order 2015. The Planning Portal publishes the current fee schedule and the application forms. England only.
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