Different people have different ways that they will go about making a workbook. The first thing you will want to do when inheriting a workbook is to unhide everything to see if the previous owner has hidden any vital data. Unhiding an Excel sheet is as easy as right clicking any tab and choosing Unhide. You can also unhide all columns and rows in a sheet by selecting the entire sheet, clicking on the cell selector, then right-click any column header and choosing Unhide.
Remove Hidden Formats
Excel has a Hidden format protection scheme that hides the formula in the Formula bar while keeping the cell visible. To view this Hidden format, you will want to unhide any hidden cells by unprotecting the sheet to view formulas. It’s important to keep in mind that some users will attempt to hide the text in a cell by making their text the same color as the background. You will want to check on this by selecting the entire sheet and then applying a new font color. This should expose any hidden text; be sure to hit the Undo button if you wish to hide everything in the way you found it. Hiding text with this way is not a best practice, if your colleague is doing this be sure to tell him to stop.
Spot Formula Inconsistencies
Be sure to pour over the formulas of your workbook and be on the lookout for inconsistencies. For example, if column K is the sum value in rows 1-10, and you see a formula that looks out of place in K5, then you will want to do some investigating to find out why. Also, be sure to look at the formulas below the data range. The contiguous formulas should all be similar in purpose.
One last thing you can do to help ensure that the formulas in place are correct, is to run a few tests with known results. For example, total up recent invoices to see if the totals you know to be correct, and the totals in the inherited Excel project, are lining up.
By looking for inaccuracies of your inherited Excel workbook, you can save yourself and everyone involved on the project a lot of time and headache from having to build off the mistakes of others.