Who prepares a viability assessment, and independence

A viability assessment in planning should be prepared by a suitably experienced valuer, normally a chartered surveyor and RICS registered valuer, working to the RICS professional statement on financial viability in planning. That statement sets mandatory requirements on objectivity, conflicts of interest and reporting, and it applies to the applicant's assessor and to the reviewer the council appoints. If you are a developer commissioning one, the person you choose and the basis on which you pay them will shape how much weight the assessment carries before a single number is read.

Councils have grown sceptical of viability evidence, and the fastest way to confirm that scepticism is to appoint someone whose independence can be questioned.

The standard that applies

The RICS professional statement on financial viability in planning sets conduct and reporting requirements for practitioners advising on viability, whether for an applicant, a landowner or a local planning authority. The practical content is about behaviour rather than method: act with objectivity and impartiality, identify and manage conflicts, do not accept instructions on terms that make the fee depend on the outcome, and disclose assumptions and their sources so that another valuer could rerun the appraisal.

The national Planning Practice Guidance on viability supplies the policy method that sits alongside it, covering benchmark land value, developer return and the treatment of planning obligations.

Neither document makes a viability assessment a legally reserved activity. Anyone can write one. But an assessment prepared by someone outside the professional framework will be given the weight the officer thinks it deserves, which in practice is very little.

What independence actually means

Independence here is not the same as neutrality about the outcome. An applicant's assessor is entitled to act for the applicant and to present the appraisal that supports the case, provided the inputs are defensible and the assumptions are stated.

What the standard prohibits is more specific. Acting where a conflict cannot be managed. Taking a success fee or any arrangement where payment rises with the level of affordable housing avoided. Allowing the client to dictate an input that the valuer does not consider supportable. Suppressing a comparable that undermines the conclusion.

The same firm cannot sensibly act for the applicant and for the authority on the same scheme, and most councils now ask both sides to confirm in writing that no such conflict exists. Our wider piece on independence and conflicts in planning evidence covers how this plays out across other specialisms, where the rules are looser and the risk is higher.

There is a softer conflict worth watching too. A valuer who acts for most of the landowners in a district and then advises its council will find their objectivity questioned at committee, whatever the paperwork says.

The applicant's assessor and the authority's reviewer

The usual pattern on a major application is two assessments. The applicant submits one. The council instructs an independent reviewer, almost always at the applicant's cost through a fee agreement signed before the review starts.

The reviewer's client is the authority. Their job is to test the applicant's appraisal, not to produce a rival scheme, and their report will usually accept large parts of the submitted work while disputing two or three inputs. Those disputed inputs are where the affordable housing number moves.

Expect the reviewer to ask for the underlying appraisal file rather than a printed summary. Refusing to provide it is a reliable way to lose the argument, because a reviewer who cannot interrogate the model will simply substitute their own assumptions.

Where the two sides cannot agree, some councils appoint a second reviewer or take the dispute to committee with both positions set out. A viability assessment that anticipates this and evidences every contested figure at the outset shortens the process considerably.

The inputs a reviewer will test

The guidance on viability describes a return in the range of 15 to 20 per cent of gross development value as potentially suitable for market housing, with a lower figure often appropriate for affordable housing delivery. Those are national reference points rather than entitlements, and a reviewer will ask why a particular figure was chosen for this scheme.

Benchmark land value is where most disputes actually live. An assessment that adopts the price the developer paid, rather than an existing use value plus premium, is not following the guidance and will be marked down.

Transparency and publication

National guidance is clear that viability assessments should be prepared on the basis that they will be made publicly available, other than in exceptional circumstances, and that even then a summary should be published in a form that allows the public to understand the conclusions.

That changes how you write. Anything you would not want a parish council reading aloud at committee should not be in the report at all. Commercially sensitive material belongs in a short annexe with a reasoned case for withholding it, not scattered through the main text.

Applicants sometimes ask whether they can submit viability evidence in confidence. The honest answer is that they can ask, and they will usually be refused.

Where assessments lose credibility

Optimistic sales values paired with pessimistic build costs, both drawn from different dates. Abnormals that appear in the appraisal but not in the engineer's report. A benchmark land value that exceeds the value the site would have with the policy-compliant scheme. Contingency counted twice, once in the cost plan and once in the profit line.

And, more often than any of these, an appraisal presented without the file behind it. Reviewers are not hostile by disposition. They are sceptical because they cannot see the working.

Reading an opposing assessment critically is a skill in itself, and our guide to reviewing a report you did not commission sets out the questions worth asking first.

Appointing and instructing

1. Ask for the valuer's RICS registration and their recent experience of schemes of your type and scale in the same market area.
2. Agree a fixed fee. Never a fee linked to the affordable housing outcome, which the professional standard prohibits and the council will ask about.
3. Confirm in writing that the firm holds no conflicting instruction for the authority or for a landowner with an interest in the site.
4. Give the valuer the cost plan, the accommodation schedule and the programme at the same time, not in instalments.
5. State in the brief that the report will be published, so the valuer writes it accordingly.

A clear written brief does more for the quality of the evidence than any amount of chasing afterwards, and our note on writing a brief for a specialist report covers what to include.

PlanScope can draft the structure and policy framing of a viability assessment as a starting point for the valuer who will sign it. For specialist technical reports, qualified professional input may be required. You can find reviewers through the professional directory.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.