Business valuation proposals are generally prepared by domain experts. They know a sector of industry and a function of management so well, that they often do not ask basic questions. They overlook, by the same token, changes in conventions to which they have become accustomed. A professional who knows the path through thorough investment analysis may ask na've questions when first introduced to a new venture, but this seeming innocence can uncover some grave and basic errors on which business valuation numbers are based.

Demand trends, competitive changes, inflation, and time lines are generally the best considered assumptions, because our minds naturally tread these areas when we reflect on business valuation. The regulatory environment, macro-economic trends, geo-political instability, and social upheavals, are some areas in which professional executives have limited if any exposure: hence assumptions remain implicit and not discussed in business valuation discussions.

It is best to take a zero tolerance approach, and to dig deeply for all assumptions in every projected value of a business valuation. Stating them is far from enough: you have to prepare models which allow you to deal with uncertainty, and to manage the risks of forward looking investments. You can prepare a fairly comprehensive list of assumptions that need examination, by listing all foreseeable risks. Expertise comes form adversity and hindsight, hence people who take the blame for past failures, can be coaxed in to invaluable insights as far as assumptions behind new business valuation is concerned.