Peer review and independent audit compared

Choosing between a peer review or an independent audit of a planning report is usually not a choice at all. A peer review is something you commission before submission, on your own terms, to find the weaknesses in your own evidence. An independent audit is something the local planning authority commissions after submission, on its terms, at your cost. One is a private rehearsal. The other is the examination.

Architects and agents who understand the difference tend to budget for both on technical schemes, because a peer review that costs a modest fee can remove the three queries that would otherwise add two months to an audit.

What each process is for

The output difference is the one with consequences. A peer review stays with you, and you decide what to act on. An audit goes on the public file, is read by objectors and councillors, and becomes the authority's evidence at any appeal. A technical criticism you could have fixed privately for a few hundred pounds becomes a paragraph in a committee report.

Who appoints and who pays

Peer review is a straightforward appointment. You choose the reviewer, agree a scope, and own the output.

Audits are less straightforward, because the authority is appointing a consultant and charging you for it, and the statutory planning fee does not cover that. The mechanisms used in practice are a Planning Performance Agreement, drawing on the power to charge for discretionary services, a separate written agreement to meet the authority's consultant costs, or occasionally an obligation in a section 106 agreement.

Three things to settle in writing before the audit starts. The scope, so the audit does not expand into a general review of the scheme. A cost estimate or a cap, because an open-ended instruction to a third party on your account is an uncomfortable position. And the identity of the auditor, so you can check for prior involvement with the site or with an objector.

Ask for the auditor's terms of reference. You are paying for the work and you are entitled to know what question they were asked.

Scope and depth

The two processes look at different things, and that is the useful part.

A peer review asks whether the evidence will survive. Is the methodology the one the authority expects. Are the inputs defensible and sourced. Does the conclusion follow. Is there a gap an objector will find. Has the report answered the policy question or only described the site. A good peer reviewer spends as much time on what is missing as on what is there.

An audit asks whether the submitted document complies. It works line by line against a methodology, checking inputs, assumptions, calculations and compliance with the relevant standard or guidance. It rarely comments on whether a different approach would have been better, because that is not the question it was given.

So a document can pass an audit and still lose the application, and it can fail an audit on three inputs while being sound in substance. Where you suspect the second, say so in the response rather than conceding the whole analysis. The dynamics of that disagreement are set out in when the council's expert disagrees with your consultant.

Where authorities require an audit

Four categories account for most audits.

Viability. National guidance on viability expects assessments to be transparent and publicly available, and authorities routinely appoint their own surveyor to review them. Expect every input to be tested: benchmark land value, build cost, sales values, finance rates and developer return. A Viability Assessment is a report where councils expect a suitably qualified author, and professional review is strongly advised in any event.

Basements and ground movement. Where a borough's published supplementary planning document requires an independent audit of a basement impact assessment, the audit is commissioned by the authority at the applicant's cost, so check the relevant document before you programme the application. Our Basement Impact Assessment page sets out the scope of the underlying report.

Technical modelling. Transport modelling, noise, air quality, daylight and sunlight, hydraulic modelling and the biodiversity metric are all audited where the outcome is contested or the scheme is large.

Heritage and design. Less often a formal audit, more often a design review panel, which operates differently again because the panel comments on design quality rather than on compliance with a method.

Programme implications

Audits take time that nobody allowed for. The authority has to appoint, the auditor has to be briefed, and the review runs while the determination period expires, which is why audited applications so often involve an agreed extension of time.

Two habits help. Offer the audit yourself at pre-application stage, so the appointment and the funding agreement are in place before validation rather than six weeks after it. And supply the model files and calculation sheets with the submission, not on request, because the single longest delay in most audits is waiting for the data behind the report.

Peer review costs programme too, but it is programme you control. A week in the diary before submission is worth more than the same week spent answering an auditor in month three.

Responding to audit queries

Respond in a table, one row per query, with the auditor's point quoted, your answer, and the document reference or the revised figure. Do not respond in prose, and do not respond by re-sending the original report with a covering letter saying it already deals with the point.

Four rules that make responses land.

1. Separate facts from judgement. Agree the facts first, explicitly, then identify exactly where the judgement differs and why.
2. Concede what is conceded. An input you got wrong, corrected openly, buys credibility for the inputs you are defending.
3. Give the working. Where the auditor cannot reproduce your number, the problem is usually a missing assumption rather than a disagreement.
4. Keep the author involved. The person who did the modelling should write the response, with the agent editing for tone rather than the reverse. The naming point in why every planning report needs a named author and date applies to responses as well as reports.

Where the disagreement persists, ask for a short technical meeting with both consultants present and the case officer in the room. Most audit standoffs are resolved in forty minutes of conversation and never would have been in six more emails.

Choosing a reviewer

For a peer review you control the choice, so use it. Four criteria.

Independence from the original author, meaning a different firm, not a different office. Relevant competence on the same document type and the same scale of scheme, evidenced by examples. Availability within your programme, because a reviewer who can start in five weeks is no use. And willingness to be named, because a reviewer who will put their name to a conclusion thinks harder than one who will not.

Brief them properly. Give them the authority's validation list, the relevant local plan policies, the report, the underlying data and any officer correspondence, and ask three questions: what would an auditor challenge, what is missing, and what would you do differently. Then be willing to hear the answer. A peer review you commission and then ignore is the most expensive document in the file.

Reviewers who can review and sign off technical reports can be found through the professional directory.

This is general guidance, not legal advice. Check audit requirements and funding arrangements with your local planning authority before relying on anything here. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.