An example
Total: 48,200. The rows above it add up to 51,450.
The total was typed in once, when it matched, and the rows have changed since.
How it happens
A total typed as a number rather than calculated. A total that adds up some of the rows but not all. A sum that takes in a subtotal as well as the rows beneath it, and so counts them twice.
Why it matters
Totals are the figures people read and quote. A wrong one is the mistake most likely to reach a client, a lender or a return.
How to find it by hand
Select the cells above a total and read the sum shown at the bottom of the window, in both Excel and Google Sheets. Compare it with the total. Repeat for every total row and column.
How Proper Spreadsheets finds it
The checker finds each row labelled as a total, adds up the numbers above it independently and reports any total that disagrees, with both figures. Only sums are compared, because a total row is not always a sum: averages and counts are left alone.
Check a whole file in seconds
Finding this by hand means reading every formula in the file. The free check reads them all, along with six other mistakes that show no error, and points to each cell. Your file is deleted as soon as the check finishes.
Other mistakes worth checking for
- A total that stops short of the data: The formula is fine. It just ends a few rows too early, and nothing on the screen says so.
- A number typed into a formula: It is right until the rate changes. Then it is wrong in every row it was copied into.
- One row that calculates something different: Every row in the column does the same thing, except one. The answer it shows looks perfectly normal.
- A figure typed over a formula: The column calculates, row after row, until the one row where somebody typed the answer in.
- Error values, and the one cell causing them: Two hundred cells show #REF!. One of them is the cause, and it is rarely the first one you see.
- A formula that points at a sheet that is gone: The cell shows 0. It should show an error, and would, if IFERROR were not hiding it.