Lawful Development Certificate (Proposed Use): Lock In Your PD Rights — 2026 Guide
In eleven London boroughs you can still convert a house into a small HMO without planning permission. That sentence sells a lot of property — and it conceals the most common mistake we see buyers make: assuming that because a conversion is generally permitted development, it is permitted development for their property. The instrument that turns that assumption into certainty is the Lawful Development Certificate for a proposed use — the "LDC (Proposed)", formally a certificate under section 192 of the Town and Country Planning Act 1990.
What it is
An LDC (Proposed) is the council's binding, written confirmation that what you intend to do would be lawful — before you do it. Like its existing-use counterpart, it is an evidential test, not a merits judgment: no neighbour consultation, no design or amenity assessment. If the proposal would be lawful, the council must certify it. For HMO work, the classic case is confirming that a C3→C4 conversion is permitted development for a specific address — but the same instrument covers any proposed use or works you believe don't need permission, from rear extensions to loft conversions (more on those below).
Where this applies — the open-market boroughs
As mapped in our complete London HMO guide, 11 boroughs remain Article 4-free for small HMOs as of June 2026: Camden, the City of London, Hackney, Hammersmith & Fulham, Harrow, Islington, Kensington & Chelsea, Kingston, Richmond, Wandsworth and Westminster. In the five area-based boroughs — Brent, Haringey, Havering, Lambeth and Southwark — the same applies outside the designated areas (our Haringey checklist shows how address-specific that check is; Havering even distinguishes by property type).
"If it's permitted development anyway, why pay for a certificate?"
Because "PD in the borough" is not "PD for your property." Four things defeat the general rule on specific sites:
Conditions on old permissions. A previous planning consent on the property may have stripped PD rights entirely — common on newer developments and conversions. Invisible until someone reads the decision notice.
The property must be a C3 dwellinghouse in lawful use. Class L doesn't apply to flats in some configurations, to properties whose lawful use is something else, or where the current use itself was never regularised.
The 6-person line. Class L covers 3–6 occupants. A layout that drifts to seven beds is sui generis — and that needs planning permission everywhere in London.
The map is moving underneath you. Hammersmith & Fulham has approved a borough-wide direction; Harrow has an immediate one in the pipeline that could take effect with no notice period. A certificated, commenced use is protected; an assumed one is not.
That last point is the strategic one. An Article 4 direction is not retrospective — but in a borough that designates after you buy and before you convert, your PD right dies with the direction. An LDC (Proposed) obtained and acted on while the right exists gives you dated, conclusive proof of where you stood — and if you complete the change of use before designation, your position is secured (then evidenced, if ever needed, via an LDC (Existing)).
There are softer payoffs too: lenders and valuers increasingly ask for certainty on HMO planning status; buyers pay more for a certificated asset; and at £305 statutory, it is the cheapest insurance in the entire transaction.
Not just HMOs — the other things an LDC (Proposed) does
The certificate covers any proposed use or works you believe are lawful without permission, and we use it well beyond C4 conversions:
Householder works — rear extensions, loft conversions and dormers, outbuildings and garden offices under Part 1 of the GPDO. The PD limits are technical (depths, heights, volume, curtilage coverage — see our householder permitted development guide), and an LDC turns "we think it complies" into proof — invaluable on resale, when buyers' solicitors ask for evidence that the loft was lawful. The fee is half the householder application fee, so the economics are trivial against the works.
Reverting an HMO to a family home — Class L works in both directions, and most Article 4 directions remove only the C3→C4 leg. A certificate confirms the reversion is lawful where that matters for a sale or refinance.
Confirming no permission is needed at all — that a proposed activity stays within the existing use class, or that a change (a home office, a lodger arrangement short of HMO use) is not a material change of use. Where the line is debatable, the certificate settles it.
What it can't do — and where people get caught: PD rights that operate through prior approval are secured by a prior approval application, not an LDC. That includes Class MA commercial-to-residential conversions and larger home extensions under the neighbour consultation scheme. Equally, flats have almost no householder PD rights, and splitting a house into flats is never PD — those routes run through full planning permission (and, for existing splits, the LDC (Existing)). Choosing the right instrument is half the value of advice here.
When to get it
Before exchange, ideally. The certificate is property-specific, so it belongs in due diligence alongside searches: it will surface stripped PD rights, use-class problems and Article 4 nuances while you can still renegotiate or walk away. Second-best is before committing to conversion works on a property you already own.
Process and cost
The application is paper-based and quicker than a planning application: site plan, floor plans, a precise description of the proposed use, and a planning analysis of why it is lawful. The fee is half the equivalent application fee — £305 for an HMO change of use from 1 April 2026, around £396 via the Planning Portal with its service charge. No consultation period, no committee.
One discipline matters above all: the certificate covers exactly what you describe. If the certified proposal says 5 occupants and you fit out for 6, or the works deviate from the certified plans, the protection evaporates. Describe the end state precisely, then build to it.
Pitfalls
Treating the certificate as planning permission — it isn't; it confirms permission isn't needed for the described proposal.
Forgetting the licensing layer — most of these boroughs run additional HMO licensing (Camden, Islington, Hackney, Wandsworth, K&C among them), so budget for the licence in parallel.
Applying with vague plans — imprecision is the main cause of refusals and of worthless certificates.
Sitting on it — a certificate confirms the law at its date. The protection comes from acting on it before the map changes.
The bottom line
Whether it's an HMO conversion in an open-market borough, a rear extension you'll one day need to evidence on resale, or a use-class question worth settling before money moves, the LDC (Proposed) is the difference between acting on a right and acting on an assumption. It is quick, cheap relative to everything else in the deal, and — with two more boroughs moving toward HMO designation — increasingly time-sensitive on the conversion side. If you're appraising a property or a project anywhere in London, contact us for a fixed-fee feasibility check: PD status, the right instrument (LDC or prior approval), the certificate, and the licensing layer where it applies.
Legal position verified 5 June 2026: s.192 Town and Country Planning Act 1990; GPDO 2015 Schedule 2, Part 3, Class L; fees per the Planning Portal schedule (1 April 2026). Borough Article 4 positions per our June 2026 verification — confirm the current position for a specific property before relying on this guide.
