Excel has often been the black sheep in disclosure. Many document exchange protocols recommend requiring spreadsheets in native format, even when the rest of the disclosure is in image format (.TIFF). The justification for this is often based upon the fact that, when printed, the formulae in a spreadsheet do not display, and spreadsheets rarely fit well on a printed page.
There is a much more sinister side to spreadsheet review: hidden content. With one right click on a column or row header, or a sheet tab, the “Hide” option can be selected, which immediately makes that content invisible on the screen. The only evidence of the disappearance is a missing column, row or sheet number, which is not that obvious in review. Granted, it just takes one right click to select “Unhide” but how often are your reviewers doing that?
Another nasty little secret in Excel is the ability to conceal the content of a single cell. This requires selecting the cell, using the “Format Cells” function, selecting “Custom”, and typing “ ;;; “ into the function box. The content of the cell disappears, but the cell remains. This is much harder to identify in review.
The good news is that this hidden content is not hidden from the indexing process, and a quick look at the extracted text will reveal what was hidden. That step is strongly recommended as part of spreadsheet review.
So, the next time you come across an Excel spreadsheet, think twice before skipping over the blank space. You may find something naughty or nice hidden there.