When to Use This Checklist
Use this checklist before sending a spreadsheet to a client, importing it into another system, building a dashboard from it, or using it for a financial decision. The goal is not to make every file perfect. The goal is to remove the common problems that silently create wrong reports.
For best results, save a copy of the original workbook first. Clean the copy, keep notes about what changed, and compare row counts before and after.
1. Audit Formulas First
Run a formula audit before editing the file. Check for broken references, hidden sheets, external links, overwritten formulas, hardcoded numbers inside formulas, and inconsistent formula patterns. Use the Spreadsheet Auditor for a fast first pass.
2. Remove Blank Rows
Blank rows split tables and confuse filters, pivots, imports, and scripts. Remove only rows that are truly blank, not rows that have a missing value in one column. The Remove Blank Rows tool helps preview the count before exporting.
3. Check Duplicates and Unique Values
Duplicate rows can inflate totals and create repeated customer records. Unique-value checks help validate category lists, region names, product codes, and IDs. Use Duplicate Row Finder and Extract Unique Values for quick checks.
4. Normalise Labels
Inconsistent labels cause reporting problems. North, NORTH, and North may be treated as different values. Use find and replace carefully, preferably with preview, before changing a whole workbook.
5. Standardise Dates and Numbers
Dates and numbers are two of the easiest places for Excel to hide problems. A date may look like 06/12/2026 but actually be stored as text. A number may look normal but fail in formulas because it came from a CSV export with hidden spaces.
Before importing or reporting, test important numeric columns with SUM, COUNT, and ISNUMBER. For dates, sort oldest to newest and look for impossible values, mixed formats, or future dates that should not exist.
6. Sort Only After Selecting the Full Table
Sorting a single column can break the relationship between rows. Always sort the full table range or use a dedicated sorting workflow. If the file is important, keep an ID column and verify rows after sorting.
7. Review Column Statistics
Column statistics reveal missing values, impossible values, and outliers. Check count, blanks, sum, average, min, max, and unique counts before reporting or importing.
8. Convert Formats Carefully
When converting Excel to CSV, JSON, or XML, confirm how dates, blank cells, numbers, and text values are handled. A clean import format is more important than a fast conversion.
9. Check Hidden Sheets and Hidden Data
Hidden sheets, hidden columns, and filtered-out rows can carry assumptions that are not obvious from the visible worksheet. Before sharing a file, check whether hidden areas contain old calculations, backup data, confidential notes, or values that still feed formulas.
10. Create a Final Review Copy
Once the file is cleaned, save a final review copy and open it again from disk. This catches issues that only appear after saving, such as broken links, external references, or formatting changes. If multiple people will use the workbook, test it on a clean machine or browser download rather than only your own editing session.
Final Rule
Clean a copy, not the only copy. Keep the original workbook untouched, export the cleaned version, and compare row counts before using the output.