2.7 Errors, auditing and trusting a spreadsheet
You can find why a number is wrong instead of overwriting it.
Before:01. Excel — First StepsUnlocks:03. Excel — Analysis
Error values are Excel telling you which kind of thing went wrong, and this topic covers reading them, tracing a wrong number back through its precedents, and stepping through a formula with Evaluate Formula. It closes the formula module because auditing is what turns formula skills into trustworthy workbooks. The confusion worth naming is IFERROR used as a blindfold: wrapping a broken formula so the error disappears is hiding a problem, not handling it. A checking column whose totals must agree is the honest alternative.
Work through these
The error values and what each one means
Each error value means something specific, and reading which one you have is the first step to fixing it rather than working around it. They are diagnostic messages rather than failures.
IFERROR and IFNA, used honestly rather than to hide problems
Wrapping a formula to suppress errors is right when you know why the error occurs and wrong when you do not. Used carelessly it converts a visible problem into a wrong number nobody notices.
Trace precedents and dependents; Evaluate Formula
The auditing tools show which cells feed a formula and which depend on it. They also let you watch a calculation happen one step at a time. This is how you find where a number went wrong.
A checking column: totals that must agree, and do
A deliberate check that two independently calculated totals agree is how spreadsheets earn trust. It is one extra column and it catches the errors nothing else would.
Practice file
- xl-03-formula-drills.xlsx
Thirty short formula tasks with a self-checking answer column that turns green when you are right.
Opens in Excel. Every name, number and address in these files is made up. No account needed to download.
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Links last checked 29 Aug 2026.
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