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Why Do Spreadsheets Need Reviewing?

More than 90% of spreadsheets have at least one error; in some circumstances, just one mistake might invalidate all the data you’ve entered into the spreadsheet.

A spreadsheet review is a great way to help reduce the chances that various errors will appear in your spreadsheet. In a large spreadsheet with tens of thousands of cells containing formulas, it is impossible for a reviewer to test and validate every cell manually.

OAK can save you time with your review process. 

Here’s how we save you time reviewing a model

Spreadsheet Review FAQ

What are the different stages of a spreadsheet review?

Initial Review

The initial review takes place before data input. It considers the role of the spreadsheet and the key expected outputs. When conducting initial assessments, you should consider the intended application of the spreadsheet and understand if a spreadsheet is the best tool for data entry.

It is essential to pay attention and focus on critical aspects that could influence the results in this phase because some components could appear unimportant the first time you look at them but become substantial in the end. You should then take a risk assessment and determine the validity of the results.

Structural Review

Following the initial review, you need to assess the spreadsheet itself. The structural review aims to provide an overview of the entire spreadsheet without getting into the details; get a sense of the overall soundness of the workbook and the risks it holds.

The activities you carry out in this phase are crucial because they show whether the spreadsheet is structurally sound and provides the correct foundations for modelling.

OAK Summarize is an excellent tool for reviewing and interpreting a model; the initial reports give you a general understanding of the reasoning behind the spreadsheet’s structure, layout, and formulas.

Data Review

The data review is where you check the inputs within your spreadsheet against external documentation. It is essential during this phase that you don’t assume anything. It can also be a good point to test inputs to ensure there aren’t any substantial flaws that might indicate a more significant problem elsewhere.

Analytical Review

You must review the spreadsheet outputs separately to determine whether they appear correct.

It is best to focus on how logically sound your data is. Does it look sensible? Do the results look plausible? If necessary, add checks that raise a red alert in response to a ratio deviating from the intended range. Some organisations have an optimism bias to check that the builder hasn’t been overly optimistic.

Charts can help make conclusions in analytical reviews more understandable. They can point to places, like some cells inside the spreadsheet, that might require further research by allowing you to spot new correlations or series of tendencies that either confirm or refute your expectations.

Analysing charts at the row level instead of the whole level is a great way to show additional information. For instance, examining income and expenses can reveal more complexity than just looking at profit.

Detailed Review

When conducting a detailed spreadsheet review, you need to ensure the steps are proportionate to the context, scale and risk of the spreadsheet. The review can include thorough testing of the formulas within your spreadsheet and checking the design principles, such as external links.

To verify formulas, you can use our Formula Walker, which facilitates formula auditing and speeds up navigation.

What to do after a spreadsheet review?

After you have finished a review, you should make corrections, record your findings and send them to the appropriate parties involved.

Occasionally, you might have to carry out a new series of reviews on the spreadsheet. Spreadsheets used for budgets, management reporting, or strategy are likely to have a longer life cycle; as such, multiple changes may occur during their lifespan.

Therefore, following each review, we recommend you to:

  • Separate your findings from the source;
  • Set a password protocol for accessing the spreadsheet components like formula cells, sheets, and files;
  • Ensure the spreadsheets are accessible to view to at least a few people;
  • Include user instructions, so it is easy for anyone to start working on the spreadsheet;
  • Properly identify the data that needs to be updated to prevent legacy values from surviving; and
  • Use data validation to stop improper inputs. The location of these cells should be made obvious via special formatting.