Many Excel worksheets are described as “models”. Sometimes (more often than not), the calculations are very hard to follow for someone who did not built the model. In such cases, it is reasonable to argue that the “model” is not a model after all. It is just a set of Excel calculations.
Excel does not miscalculate, so any spreadsheet will show correct figures. For these figures to be a model, they need to be a representation of a real-life situation. Where the worksheet items are clearly labelled, and there is a clear and transparent logic flow, then it should be possible to identify the corresponding situation(s) in real-life to which the calculations correspond (e.g. a multiplication of two numbers could correspond to the calculation of sales revenue from the unit price and the volume sold). Alternatively, if the labelling and flow is not particularly clear, but sufficient detailed supporting documentation is provided which explains the calculations as they correspond to a real-life situation, then one may consider that the calculations also form a model.
There are unfortunately far too many cases where people who are in principle highly skilled in Excel create “models” which are neither documented nor understandable by others (even others within their organisation who are working on the same project!). It should be incumbent on anyone who wishes to be considered as a competent modeller (rather than having competence in Excel) to create transparency in their work, making it as easy as possible to understand to others. All too often, it is the fate of the recipient to try to make head or tail of something that does not deserve the label of “model”, but who is left in the situation of feeling inadequate or lacking knowledge for not being able to interpret the model. In reality, due to the number of combinations of possible formula and calculations that are possible to create in Excel, it is relatively easy to create a set of calculations that correspond to a real-life situation but which no-one, however smart, would be able to correctly identify or be able to judge to be correct or not.
As a modelling community, I believe that we need to create an environment of push-back, where these poor “models” are not considered as models, but only as a “set of calculations (of something)”. We need to help to create a cultural environment within companies that allows such work to be sent back for rework!!