Errors that hide.
FORMULA RANGES NOT COVERING ALL THE DATA
Rows added below a total are excluded.
TEXT STORED AS NUMBERS, OR NUMBERS AS TEXT
Sums ignore text. Check the alignment: numbers align right by default.
DATES NOT RECOGNISED AS DATES
They sort alphabetically, and cannot be calculated with.
LEADING ZEROS REMOVED
Reference codes destroyed on import. Format the column as text first.
LONG NUMBERS CONVERTED TO SCIENTIFIC NOTATION
The same problem, with account and phone numbers.
SORTING PART OF A RANGE
Data separated from its own rows.
HIDDEN ROWS INCLUDED IN TOTALS
Filtered views still sum what is hidden, depending on the function used.
COPYING A FORMULA WITHOUT FIXING REFERENCES
References shift, silently producing wrong results.
ROUNDING AT DIFFERENT POINTS
Totals that do not match.
WHAT CATCHES MOST OF THESE
Comparing against a known figure, and checking the row count.
WHAT TO DO BEFORE TRUSTING ANY SPREADSHEET
Both of those.
