The 20% Buffer Has Arrived: What the July 2026 Housing Land Supply Change Means for Land Teams
A practical guide to the 20% five-year housing land supply buffer applying from 1 July 2026, which authorities it affects and how land teams should review their pipeline.
8 min
The five-year housing land supply calculation changed on 1 July 2026 for a specific group of English local planning authorities. It is not a blanket change everywhere, and it does not automatically make every unallocated site acceptable. But for land teams working across several authorities, it is important enough to trigger an immediate review of the opportunity book.
From 1 July, a 20% buffer applies for decision-making where an authority has a housing requirement adopted in the previous five years, that requirement was examined against a pre-12 December 2024 version of the National Planning Policy Framework, and its annual requirement is less than 80% of the latest standard-method local housing need figure. The government’s housing supply guidance now states this directly.
This is an additional route to a 20% buffer. The existing Housing Delivery Test route still matters: the same guidance applies a 20% buffer where delivery over the previous three years was below 85% of the requirement.
That is a technical sentence with a commercial consequence: an authority’s claimed supply can tighten without a single consent lapsing or a single housing trajectory changing.
What the buffer actually changes
A buffer increases the number of deliverable homes an authority needs to identify for the five-year period. It does not increase the underlying annual housing target. National guidance says buffers are intended to improve the realistic prospect of achieving supply; the 5% buffer also exists to ensure choice and competition in the market for land.
Suppose an authority needs to demonstrate 10,000 homes over five years before any shortfall is addressed. A 20% buffer increases the relevant requirement to 12,000. The deliverable supply has not changed; the denominator has.
That can reduce the number of “years” of supply the same site trajectory represents. Bristol’s local-plan examination material gives a useful illustration. One published calculation moved from 6.59 years to 5.49 years when the 20% buffer was applied, using the figures in that assessment. That does not mean every authority will cross below five years, but it shows why teams should recalculate rather than rely on last quarter’s headline.
Which authorities should land teams review?
Do not start with a national list copied from a newsletter. Start with the evidence for each authority in which you hold or pursue land.
For every relevant LPA, record:
the adopted housing requirement and adoption date;
which NPPF version was used at examination;
the latest standard-method local housing need figure;
whether the adopted annual requirement is below the 80% threshold;
the authority’s latest five-year supply position;
the base date and publication date of that position;
the treatment of shortfall, buffer and deliverability;
any local-plan examination statements published since the headline position;
relevant appeals that test the authority’s case.
The trigger is not simply “old plan” or “low supply”. All parts of the national policy test matter.
Why the published headline may be stale
Housing land supply is unusually sensitive to dates and assumptions. A council webpage may display a figure based on a report with an earlier base date. A local-plan examination note may contain a newer trajectory. An appeal decision may test deliverability assumptions that are not reflected in the headline. Sites counted at adoption may slip, stall or change capacity.
The operational mistake is to store “5.4 years” as a permanent field. A useful land system stores the claim, its source, its date and the assumptions underneath it.
That means keeping the actual document and recording:
what period the calculation covers;
which sites make up the claimed supply;
the expected delivery by year;
whether major sites have detailed permission, outline permission, allocation only or no permission;
the evidence relied upon for delivery;
disputed lapse rates, lead-in times and build-out rates.
The number is the conclusion. The site schedule is the evidence.
Does a shortfall mean permission will be granted?
No.
Where the relevant policies are out of date, the presumption in favour of sustainable development can become important. But decision-makers still assess the development plan, protected assets, flood risk, Green Belt policy, design, highways, ecology, infrastructure and the other material considerations applying to the site.
A weak site does not become a good site because an authority cannot demonstrate five years. A strong site may become more strategically valuable because the balance changes.
This distinction matters when speaking to landowners. “The council is below five years, therefore this land will get permission” is not a responsible message. A better explanation is:
The authority’s housing supply position may strengthen the planning case, but the site still has to survive its own policy and constraint assessment.
The immediate portfolio review
Land teams should divide their holdings and pipeline into four groups.
1. Live applications and appeals
Recheck the latest supply evidence, the correct buffer and any post-submission changes. Make sure the planning statement is using current evidence rather than the figure available when the application was prepared.
2. Promoted but unallocated sites
Re-score sites that are sustainable, well related to settlements and capable of addressing an emerging shortfall. Update delivery evidence: ownership control, access, infrastructure, technical work and a credible programme all matter.
3. Previously rejected opportunities
Look again at sites rejected mainly because timing, policy weight or housing need was unfavourable. Do not reopen sites ruled out by an immovable constraint without new evidence. The point is to find changed decisions, not to repeat old optimism.
4. Early pipeline and landowner approaches
Adjust priority by authority and settlement. A changed supply position may justify earlier contact or technical spend, but only after the site-level screen.
What a good reappraisal contains
The reappraisal should be short enough to use and detailed enough to audit.
Include:
Current policy position. Adopted plan, emerging plan stage, NPPF position and relevant neighbourhood plan.
Five-year supply evidence. Source, base date, claimed figure, applicable buffer and confidence.
Site relationship. Settlement hierarchy, services, transport and relationship to the built form.
Constraints. Green Belt or grey belt, flood risk, heritage, ecology, landscape, access, utilities and other designations.
Deliverability. Control, access, technical work, infrastructure, programme and likely market delivery.
Change since last review. The evidence that justifies a different decision.
Decision. Pursue, hold, reject, reappraise or proceed subject to named evidence.
The final point prevents a research note becoming another document nobody acts on.
Why this is an information-management problem
The calculation itself is not difficult. The difficulty is maintaining the inputs across dozens of LPAs and hundreds of opportunities.
The relevant evidence arrives through council webpages, PDFs, examination libraries, appeal decisions, consultant notes and emails. One person remembers that an authority’s trajectory changed. Another has the updated spreadsheet. The pipeline still shows the conclusion from six months ago.
That is exactly where a firm-specific AI system is more useful than a generic chatbot. The job is not to explain five-year supply in the abstract. It is to connect the current policy evidence to your sites, your prior decisions and your next actions—without losing the source.
Harold is configured around a firm’s own pipeline, documents and appraisal process. It can help the team identify which sites depend on an outdated assumption, assemble the evidence for review and record why the decision changed. The planning judgement remains with the team.
The practical conclusion
The 1 July change should trigger a targeted review, not a national land grab.
Start with the authorities where the new 20% buffer applies. Verify the latest evidence. Recalculate the position. Then reopen only the sites whose planning balance or commercial priority may genuinely have changed.
Policy changes create value when they reach the opportunity record. Until then, they are just another PDF.
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