Open both Excel sheets
Make sure the data ranges are aligned
Use conditional formatting to highlight differences
Use formulas like `=A1=B1` to compare cells
Use `IF` to return matching or different values
Use `VLOOKUP`, `XLOOKUP`, or `INDEX-MATCH` to compare rows across sheets
Use `COUNTIF` to find missing or duplicate values
Use `Power Query` to merge and compare tables
Use `Spreadsheet Compare` if available in Microsoft Office
Sort both sheets by the same key before comparing
Compare row counts and column counts
Check for differences in formatting if needed
Save a backup before making changes