Who prepares a viability assessment and to what standard
A viability assessment is prepared under a mandatory professional standard that requires objectivity, declared conflicts and transparent inputs. It is not an advocacy document.
Who prepares a viability assessment is a question with a short answer and a long one. The short answer is a chartered surveyor or development consultant working to the RICS professional statement on assessing viability in planning. The long answer is that the standard imposes duties of objectivity and impartiality that change what the author can do for the client, and those duties are what an authority's reviewer will test first.
A viability assessment is not an advocacy document. The professional statement is explicit that the practitioner acts with objectivity even where instructed by one party.
The professional standard that governs the work
The RICS professional statement on assessing viability in planning sets mandatory requirements for members and regulated firms. Those requirements cover objectivity and impartiality, the identification and management of conflicts of interest, transparency of inputs and assumptions, and the form of the report itself.
They are mandatory. A member who ignores them risks disciplinary action, and a reviewer who spots a departure has a straightforward basis on which to recommend that the assessment be given little weight.
That matters commercially. An assessment prepared outside the standard, by someone without the relevant membership, invites the authority to dismiss it without engaging with the numbers. A Viability Assessment is one of the report types where authorities expect a suitably qualified author, and professional review is strongly advised before submission.
Who can author one
Practically, the author is a chartered surveyor with development appraisal experience, usually a registered valuer where valuation opinions are being given. Development consultants and planning consultants with appraisal skills also prepare them, but the authority will look for the professional standard to have been applied regardless of the author's title.
Specialist inputs sit underneath. Build cost from a quantity surveyor or a published cost database, sales values from local comparable evidence, affordable housing values from a registered provider bid or a local transfer price, finance assumptions from the actual facility where one exists.
The author's job is to assemble those inputs, test them and present them transparently. Where an input is contested, the report should say so and show the sensitivity rather than presenting a single number. And where a figure comes from a single source, name the source in the table rather than in a footnote.
Transparency and the expectation of publication
National planning practice guidance is clear that viability assessments should be prepared on the basis that they will be made publicly available, other than in the limited circumstances the guidance describes, and that even then the key inputs should be published.
Write the assessment accordingly. Commercially sensitive material does not belong in the main report, and an author who assumes confidentiality produces a document the authority cannot use. Where a redaction is sought, the reasons have to be set out and the authority decides.
This expectation has a second effect worth naming. Because the document will be read by objectors, members and the local press, the arguments in it have to survive non-expert scrutiny. A report that is defensible to a valuer but incomprehensible to a committee is only half finished.
Benchmark land value and how it is established
Benchmark land value is the figure the residual value is compared against, and it is where most disputes live. Guidance establishes it on an existing use value plus a premium basis, with the premium reflecting a reasonable incentive for a landowner to bring the site forward, taking account of policy requirements.
Two points follow and both are routinely argued.
The premium is not a market land price. A price paid for the site that assumed no policy compliance does not set the benchmark, and guidance says land value should reflect emerging policy requirements. Overpaying for land is not a viability argument.
Existing use value means the value in its existing use, not its hope value. On a site with an extant consent the position is more involved, and benchmark land value where the site already has consent is worked through separately.
The inputs that get challenged
| Input | Common challenge |
|---|---|
| Gross development value | Comparable evidence too distant, too old or from a different product |
| Build cost | Allowances for abnormals unevidenced, contingency stacked on contingency |
| Developer return | Return taken on cost and value inconsistently, or above the guidance range |
| Affordable housing value | Transfer price below local registered provider bids |
| Finance | Rate and term not matched to an actual facility |
| Programme | Sales rate pessimistic, build period extended without evidence |
| Benchmark land value | Based on price paid rather than existing use value plus premium |
Guidance sets out an indicative range for developer return on market housing and a lower figure for affordable housing, so a return outside that range needs a reason specific to the scheme. Abnormals are the other recurring fight: they have to be evidenced by the ground investigation, the structural survey or the utility quotations, not asserted as a round sum.
Sensitivity testing is how a serious report handles that uncertainty, and the method behind sensitivity testing in a viability appraisal is set out separately.
The authority's reviewer and who pays
Authorities almost always appoint an independent reviewer, and the applicant almost always pays, usually through a side agreement signed before the review starts. Budget for it and for the time it takes, because the review runs as a sequence rather than a single exchange. Report, then questions, then responses, then a draft review, then comments, then the final review. Six steps, each with a gap in it, and on a contested scheme the whole cycle can take longer than the determination period the application is nominally running to.
The reviewer's role is to test the inputs and the method, not to negotiate. Where positions remain apart, some authorities hold a round-table meeting with both appraisers, which is usually faster than three more rounds of correspondence. The scope of an independent review of a viability appraisal is covered separately.
Review mechanisms are a separate thing again. Where viability is accepted at submission, a section 106 obligation often builds in an early or late stage review to capture improved values, and the trigger points and formula are negotiated rather than standard.
Conflicts, declarations and how to instruct
The professional statement requires conflicts to be identified and managed, and declarations to appear in the report. An author who has acted for the landowner on the acquisition, or who is advising on the disposal, has something to declare.
Instruct with the policy test in mind. Tell the author which policy requirement the scheme cannot meet, what the development plan says about viability, what the authority's supplementary guidance requires, and whether a plan-wide viability study underpins the policy. That last point matters: where the policy was tested at plan-making stage, the guidance expects the decision-taking assessment to explain what has changed on this particular site. An appraisal produced without that framing answers a question nobody asked.
Finally, appoint early. Viability is often treated as something to run after the scheme is designed, and by then the design decisions that drive cost and value are fixed. Where the question is whether a scheme can carry its policy obligations, the appraisal belongs alongside the first massing study. If you want a reviewer to sign off a draft, the professional directory is the route to a review request.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Does a viability assessment have to be written by a chartered surveyor?
In practice yes, and usually by a registered valuer where valuation opinions are given. Development and planning consultants also prepare them, but authorities look for the RICS professional statement on assessing viability in planning to have been applied whatever the author's title. An assessment prepared outside that standard invites the authority to give it little weight.
Will my viability assessment be published?
National planning practice guidance says assessments should be prepared on the basis that they will be made publicly available, other than in limited circumstances, and that key inputs should be published even then. Write the report accordingly, keep commercially sensitive material out of the main document, and set out the reasons for any redaction you seek.
Does the price I paid for the land set the benchmark?
No. Benchmark land value is established on an existing use value plus a premium basis, with the premium reflecting a reasonable incentive for the landowner to bring the site forward while taking account of policy requirements. A price paid on the assumption that policy obligations would not be met does not set the benchmark.
Who pays for the council's independent review?
The applicant, almost always, under a side agreement signed before the review begins. The reviewer tests the inputs and the method rather than negotiating. Budget for the sequence as well as the fee: report, questions, responses, draft review, comments and final review each take time, and a round-table meeting is often faster than further correspondence.
What is a review mechanism in a section 106 agreement?
A clause requiring viability to be retested at a defined point, commonly before implementation or after a set proportion of sales, so that improved values can be captured as additional affordable housing or contributions. The trigger points, the formula and any cap are negotiated on each scheme rather than being standard.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.