RICS Rules of Conduct and Global Professional Standards RB-VPS2: Red Book VPS 2: bases of value, assumptions and special assumptions

The valuer must choose a basis of value appropriate to and consistent with the purpose and state it (or its definition) in the terms and report; a basis not defined in the standards must be defined, stated and, if its use is voluntary, flagged as a departure with an explanation of why a recognised basis was unsuitable; assumptions and special assumptions differing from a market value estimate must be distinguished. Assumptions must be reasonable and relevant and settled with the client, ideally within the engagement terms, and revisions discussed and recorded before the report; special assumptions must be realistic, pertinent and sound, and expressly agreed and confirmed in writing before the report is issued, and referred to in any published reference; marketing constraints must be agreed and described precisely, the phrase 'forced sale value' is banned, and assumptions about projected values must be agreed and the greater uncertainty noted.