Courts generally allow a competent valuer a margin of around ±5% for a straightforward residential property, widening to ±10% or more for unusual or hard-to-value properties. A valuation only becomes negligent when it falls outside the reasonable range and the valuer's methodology fell below competent standards. Establishing both is the expert witness's task.
For contested valuation evidence, courts and tribunals expect an RICS Registered Valuer reporting to Red Book standards — an unregistered opinion invites immediate challenge on qualification. All Survey Merchant valuation experts are Registered Valuers, and every report carries the CPR Part 35 declaration and statement of truth.
One valuer instructed jointly by both parties, reporting to the court rather than to either side — the family courts' strong preference in matrimonial financial proceedings, and common in probate and TOLATA disputes. Fees are normally shared. The SJE inspects once, answers both parties' questions in writing, and their figure usually becomes the working value in the case.