This study uses valuations and sales data from the Investment Property Databank UK
Monthly Index to attempt to identify the date that sale data is divulged to valuers. This
information will inform accuracy studies that use a cut-off date as to the closeness of
valuations to sales completion date as a yardstick for excluding data from the analysis. It will
also, assuming valuers are informed quickly of any agreed sales, help to determine the actual
sale agreed date rather than the completion date, which includes a period of due diligence
between when the sale is agreed and its completion. Valuations should be updated to this
date, rather than the formal completion date, if a reliable measure of valuation accuracy is to
be determined.

An accuracy study is then undertaken using a variety of updating periods and the differences
between the results are examined. The paper concludes that the sale only becomes known to
valuers in the month prior to the sale taking place and that this assumes either that sales due
diligence procedures are shortening or valuers are not told quickly of agreed sale prices.
Studies that adopt a four-month cut-off date for any valuations compared to sales completion
dates are over cautious, and this could be reduced to two months without compromising the
data.