Migrating Your Reports from Excel to Power BI: Data Source Audit is a Key Step

Before migrating your Excel reports to Power BI, auditing your data sources is a crucial step that is often overlooked. This preliminary analysis determines the success of your migration.

Why Audit Before Migrating?

Many migration projects fail because they underestimate the complexity of existing data sources:

• Scattered data across multiple Excel files
• Complex formulas difficult to reproduce
• Broken or outdated links
• Manual data that is not traceable

Audit Steps

1. Source File Inventory

List all Excel files involved in your reports:

| File | Location | Update Frequency | Owner | |------|----------|------------------|-------| | Budget_2024.xlsx | SharePoint Finance | Annual | Controlling | | Monthly_Sales.xlsx | C: Drive | Monthly | Sales | | Customer_Master.xlsx | Email | Ad hoc | CRM |

2. Data Flow Mapping

For each report, identify:

• Where does the data come from?
• What transformations are applied?
• Who updates it and when?
• What are the dependencies?

3. Formula and Calculation Analysis

Document complex Excel formulas:

=SUMIFS(Sales[Amount],Sales[Region],"France",Sales[Date],">="&DATE(2024,1,1))

These formulas will need to be converted to DAX:

France Sales 2024 =
CALCULATE(
    SUM(Sales[Amount]),
    Sales[Region] = "France",
    YEAR(Sales[Date]) = 2024
)

4. Data Quality Assessment

Check for each source:

• [ ] Complete data (no missing rows/columns)
• [ ] Consistent formats (dates, numbers, currencies)
• [ ] No duplicates
• [ ] Outliers identified
• [ ] Standardized naming conventions

Key Questions to Ask

About Sources

1. Is this source reliable? (official source system vs manual extraction)
2. What is the update frequency? (real-time, daily, monthly)
3. Who is responsible for the data? (identified owner)
4. Are there alternatives? (API, direct database connection)

About Transformations

1. Are the calculations documented?
2. Are there implicit business rules?
3. Are the formulas auditable?
4. Can manual transformations be automated?

About Users

1. Who uses this report?
2. What are the real needs?
3. Which features are essential?
4. What level of autonomy do they want?

Decision Matrix: Migrate or Rebuild?

| Criterion | Migrate As Is | Rebuild | |-----------|---------------|---------| | Reliable and documented sources | ✅ | - | | Undocumented complex calculations | - | ✅ | | Manual data | - | ✅ | | Report stable for a long time | ✅ | - | | Evolving user needs | - | ✅ | | Siloed data | - | ✅ |

Post-Audit Action Plan

Scenario A: Direct Migration

If your sources are healthy:

1. Connect Power BI to Excel sources
2. Recreate calculations in DAX
3. Reproduce visuals
4. Test with users

Scenario B: Source Rebuild

If sources are problematic:

1. Centralize data in a Lakehouse or SQL database
2. Automate data feeds
3. Create a clean data model
4. Build new reports

Audit Deliverables

At the end of the audit, you should have:

• Complete inventory of data sources
• Mapping of flows and dependencies
• List of formulas to convert to DAX
• Data quality report
• Recommendations (migrate vs rebuild)
• Effort and timeline estimate

Conclusion

Auditing data sources is an investment that secures your migration project. Don't skip it, even if you're eager to see your first Power BI dashboards.

A well-conducted audit prevents unpleasant surprises and lays the foundation for a successful migration.

Need help auditing your data sources? Book a free diagnostic