How to audit Excel formula changes

A changed number does not always mean a changed formula, and a changed formula can be more important than many changed numbers. Review the formula map first so model logic is not hidden by normal period-to-period movement.

Freeze the two workbook versions before comparing

Save a named before-and-after version, record the reporting cutoff, and preserve a hash for each file. This prevents a reviewer from comparing a refreshed workbook against a moving target or an unsaved local edit.

Save both files as XLSX.
Record the purpose and reporting period of each version.
Keep the source hashes with the review evidence.

Separate formula changes from changed values

Formula differences show that workbook logic, references, or constants were edited. Value differences can arise from source data or recalculation even when the formula text is identical. Treat these as different review queues instead of one large list of changed cells. For example, =SUM(B2:B4) versus =SUM(B2:B5) is a formula exception even if cached values happen to match. ExactDiff compares formula text across worksheets, does not recalculate Excel formulas, and applies the 30 MB compressed, 150 MB expanded XLSX limits.

Prioritize changes that can alter control logic

Review removed formulas, new hard-coded constants, altered ranges, and changed absolute or relative references before routine copied formulas. A single changed lookup range or error-handling branch can affect an entire model even when the displayed values still look plausible.

Keep a reproducible exception record

Export the formula exceptions, record which changes were approved, and link the review to the two source hashes. Material workbooks still need an independent business review; a formula diff makes that review targeted and repeatable.