Two homeowners apply for what looks like the identical certificate, confirming a rear extension is lawful, and one pays £548 while the other pays £274. Neither figure is wrong. The difference comes down to timing: whether the extension already exists or hasn’t been built yet, a distinction that changes the fee by exactly half.
What this certificate actually confirms
A Lawful Development Certificate doesn’t grant planning permission. It confirms, formally and in writing from the council, that something either didn’t need planning permission in the first place, or has been in place long enough to become immune from enforcement action. It’s proof, not permission, and the two get confused more often than the distinction really allows for.
Three different scenarios, three different calculations
- Existing use or operation, something already built or already in use: charged at the full reference fee, the same amount that would have applied had a planning application actually been required for that development
- Existing use, lawful despite not complying with a condition or limitation: a flat £309
- Proposed use or operation, not yet carried out: charged at half the reference fee
Why “the reference fee” isn’t always £548
This is the detail that trips up most explanations of LDC cost. The certificate fee is pegged to whatever the equivalent planning application would have cost for that specific development, not a fixed universal figure. For a typical single-dwelling extension, that reference fee is £548, the householder rate, making an existing-use certificate £548 and a proposed-use certificate £274. But for a larger commercial building, or a scheme involving multiple dwellings, the reference fee follows whatever banding would genuinely have applied to that development instead. A certificate covering something equivalent to a 12-dwelling scheme, for instance, would reference the £659-per-dwelling full application rate, not the householder figure at all.
Why proposed costs exactly half of existing
The logic sits in what the council actually has to assess. Confirming something already built is lawful involves verifying real, physical evidence against the rules that applied at the time. Confirming a proposed but not-yet-built project would be lawful is a comparatively simpler desk exercise, checking the plans against current permitted development rules, without any site inspection of completed work. The lower assessment burden is reflected directly in the fee.
The non-compliance certificate, a different situation entirely
The £309 flat fee covers a genuinely distinct scenario: confirming it was lawful not to comply with a specific condition or limitation attached to an existing use, rather than confirming a use or operation itself is lawful. This doesn’t scale with the reference fee the way the other two categories do, because it isn’t assessing an entire development, just whether one particular condition breach was actually lawful. Worth noting too, this fee is added on top of any other fee due if it’s combined with a separate application, rather than replacing it.
Why people apply even when they don’t strictly have to
Permitted development rights already cover a large share of extensions, loft conversions, and similar projects, meaning no planning application, and technically no LDC, was ever required. Homeowners apply anyway, because a certificate provides something a permitted development project otherwise lacks: formal, council-issued proof. Solicitors, mortgage lenders, and future buyers frequently ask for exactly this kind of documentation during a sale, and “it was permitted development, trust me” doesn’t carry the same weight as an actual certificate.
A four-year clock that matters for existing-use certificates
For most operational development, building work, an existing-use certificate generally requires the work to have been substantially complete for at least four years without enforcement action being taken (different, longer timeframes can apply to certain changes of use). This isn’t a technicality. A certificate application submitted too early, before that period has genuinely elapsed, can be refused on that basis alone, regardless of how clearly permitted development rules would otherwise have applied.
A worked comparison across the two main routes
A homeowner built a single-storey rear extension eighteen months ago, believing it fell under permitted development. Because it’s been less than four years, an existing-use certificate isn’t yet available; the immunity period hasn’t elapsed.
A different homeowner is planning an identical extension but hasn’t started work. They apply for a proposed-use certificate instead, referencing the same £548 householder rate that extension would carry, at half that amount: £274. Confirmation arrives before a single brick is laid, giving genuine certainty rather than an assumption resting on planning rules being correctly understood.
Where this fits alongside other application types
An LDC is fundamentally different from a householder application, which seeks permission for work that does need it. It’s also distinct from Prior Approval, which covers a specific, defined set of permitted development categories with their own separate process entirely. An LDC sits apart from both: not seeking permission, but formally confirming that permission was never the requirement in the first place.
For the official guidance on Lawful Development Certificates, see Planning Portal. For the current fee schedule, see Gov.uk: Fees for planning applications.
Not sure which certificate type applies to your situation, or what the reference fee works out to? Use the calculator to confirm.