Most spreadsheets don’t become unreliable overnight.
Unreliability is usually the result of small decisions that accumulate over time.
At the beginning, everything works.
Over time, however, the structure becomes harder to manage, and the file begins to behave unpredictably.
The following are some of the most common causes:
1. Uncontrolled Data Entry
Free text, inconsistent formats, and uncontrolled input introduce inconsistencies that propagate across the entire file, including calculations.
Over time, data quality deteriorates.
2. Deletion or Corruption of References
Deleting cells, columns, or sheets referenced in formulas can silently break logic.
Errors often appear later, in places that are difficult to trace.
3. Using Ranges Instead of Structured Tables
Using simple ranges instead of structured tables makes maintenance more difficult and increases the risk of errors.
Formulas become more vulnerable to changes, and scaling the file becomes unpredictable.
4. Use of Volatile Functions
Functions such as TODAY(), NOW(), INDIRECT(), and OFFSET() increase recalculation load, affecting performance and introducing unpredictable behaviour.
In large files, this impact becomes particularly noticeable.
5. Mixing Data Input and Outputs
When data is entered and processed in the same area, the structure becomes difficult to understand and control.
Separating inputs and outputs is essential for the stability and reliability of the file.
6. Lack of Version Control
Multiple versions of the same file create confusion and increase the risk of working with outdated or incorrect information.
The absence of clear version control makes it difficult to track changes.
7. Hidden Dependencies Between Files
When a spreadsheet depends on data from external files, hidden dependencies are introduced that are not immediately visible.
Without proper structure, these links can break, causing data to become outdated or inconsistent.
What This Means
These issues rarely appear in isolation.
They often combine, gradually turning spreadsheets into systems that become unreliable and eventually fragile.
At this point, the file stops being a tool you can rely on.
A first step
If your Excel files are becoming slow, unreliable, or difficult to manage, a short audit can help identify the underlying issues and their root cause.
No changes.
No commitment.
Just a clear picture of what is happening.