How to Prepare for a VAT Audit

VAT audits don’t usually uncover tax problems, they uncover data problems.

When businesses receive notification of a VAT audit, the immediate assumption is often that the challenge will be interpreting complex VAT legislation. In reality, that is rarely the biggest issue.

Most organisations understand the VAT rules that apply to their business. The real difficulty is proving that those rules have been applied consistently across thousands or even millions of transactions.

By the time an audit begins, finance teams are often trying to answer questions such as:

• Why does this transaction have a different VAT treatment?
• Why can’t this VAT return be reconciled back to the General Ledger?
• Why was reverse charge VAT applied to some invoices but not others?
• Why is supporting evidence for cross-border transactions incomplete?

These aren’t tax technical questions, they’re questions about data integrity, ERP configuration and process governance.

For businesses running SAP or other enterprise ERP systems, VAT audits have become increasingly data-driven. Tax authorities are no longer sampling a handful of invoices; they increasingly expect businesses to demonstrate that VAT is calculated consistently and that every figure reported can be traced back to the underlying transaction.

Where VAT audit issues typically arise in ERP systems

VAT audit findings are rarely isolated mistakes. They usually reflect systemic weaknesses that repeat across large volumes of transactions.

A key driver is tax determination logic. When VAT rules are incorrectly configured, or when manual overrides are permitted, the system can consistently apply incorrect treatment without immediate visibility. This becomes particularly exposed in areas such as reverse charge transactions and cross-border services, where small configuration gaps scale quickly.

Another common issue is master data integrity. VAT treatment is heavily dependent on customer and vendor settings. If this data is incomplete or inconsistent, the system will produce inconsistent VAT outcomes even when tax logic itself is correct.

Finally, reporting and control gaps often complete the picture. Even where VAT is calculated correctly, issues arise when outputs are not regularly reconciled or when exceptions are not actively monitored.

Typical control breakdowns include:

• VAT outputs not reconciled to accounting records
• Exception transactions not reviewed during the period
• Manual adjustments made outside controlled workflows

Individually, these issues may appear minor. Combined, they create systemic audit exposure.

Introducing a controlled VAT framework: determination and reporting together

To address these challenges, we typically see the need for a structured approach built around two integrated capabilities:

• VAT Determination Solutions (how the VAT is determined in the ERP system)
• VAT Reporting Solutions (how VAT is validated, reconciled, and evidenced)

When these operate together, VAT becomes fully system-driven rather than manually interpreted.

This means:

• Every transaction follows defined tax logic
• Every VAT outcome is traceable to source data
• Every reporting figure is generated from controlled system outputs
• No spreadsheet-based reconstruction is required for audit purposes

In effect, audit readiness becomes a by-product of system design rather than a separate exercise.

The reconciliations auditors expect (and systems should already produce)

Even in a controlled environment, auditors will still test whether VAT figures reconcile back to underlying records. The key difference is that this should not require manual assembly.

At a minimum, businesses should be able to demonstrate alignment between:

• VAT returns and the General Ledger
• Output VAT and sales invoice data
• Input VAT and purchase invoice data
• VAT codes and underlying tax determination logic
• Cross-border reporting (OSS/IOSS) and transactional records  if applicable

In a mature framework, these are not audit tasks. They are continuously available system outputs.

A real-world example of ERP-driven VAT exposure

A recent client example we assisted on highlights how quickly a small configuration issue can escalate into material tax risk.

A UK-established business was purchasing services from a German supplier. Due to incorrect tax determination settings in their ERP system, it treated these transactions as domestic purchases of German goods rather than cross-border services.

As a result, German VAT was incorrectly posted as recoverable input VAT, and the UK reverse charge mechanism was not applied.

Because this logic was embedded in system configuration, the error was replicated automatically across all relevant transactions over an extended period. By the time it was identified, the business had incorrectly offset German input VAT resulting in significantly under declaring their German VAT liability with penalties and interest also imposed.

The critical point is that there was no misunderstanding of VAT legislation. The issue was the absence of controlled, validated VAT determination logic within the ERP environment.

What VAT audit readiness looks like in practice

In mature organisations, VAT audit readiness is not a reactive process. It is embedded into daily ERP governance.

This typically includes:

• Controlled VAT determination logic within ERP configuration
• Tax code definitions and determination rules
• Customer and supplier VAT validation status
• Ongoing validation of master data quality
• Automated exception monitoring
• Exception logs and override history
• Regular reconciliation of VAT outputs to accounting records
• Formal change control for tax configuration updates
• Configuration change records

In this environment, VAT is not managed as a separate compliance activity. It is an outcome of controlled system design.

The underlying issue: ERP calculates VAT, but spreadsheets validate it

In many organisations, VAT determination happens inside the ERP system, but validation still happens externally in spreadsheets.

This creates a structural gap between system execution and audit evidence. It leads to delayed reconciliations, fragmented audit trails, and reactive investigation during audit periods.

By contrast, a controlled VAT framework, such as Meridian’s ARCO Determination and Compliance solution ensures that calculation, validation, and reporting exist within a single governed environment removing the need for external reconciliation layers entirely.

Final thoughts

VAT audits are becoming increasingly data-driven, with a strong focus on system integrity rather than isolated transactional errors.

The organisations that experience the least disruption are those that move away from fragmented processes and toward integrated VAT control frameworks, where determination and reporting operate as a single governed system.

When that structure is in place, VAT is no longer something reconstructed during an audit. It is something that can be demonstrated continuously, with full traceability and no manual intervention required.