What is Compliance-at-Source?

In indirect tax, most compliance failures are not the result of ignorance — they are the result of architecture. A transaction happens, VAT is calculated too late, too manually, or by the wrong system, and by the time the error surfaces it has replicated across dozens of documents. Compliance-at-source is the architectural answer to this problem.

The Traditional Approach: Post-Processing

Traditional indirect tax processes work in layers separated from the originating transaction. An ERP system creates a purchase order or sales invoice, often with a placeholder tax code. A separate tax engine — sometimes a third-party cloud service — is then called via an API to validate or recalculate the tax. In some organisations, tax determination is reviewed manually by the tax department at month-end, long after the underlying documents have been posted.

This separation creates systemic risk. If the API call fails, tax defaults to zero or to a catch-all code. If the month-end review finds an error, undoing it requires finance effort and may trigger audit flags. The further tax determination is from the transaction, the harder it is to correct — and the more likely errors are to compound across related documents.

The Compliance-at-Source Model

Compliance-at-source reverses this architecture. Tax determination logic is embedded directly in the transactional layer — inside the ERP system itself, executing at the moment the document is created. When a user raises a purchase order in SAP, the correct VAT treatment is determined in the same process step, using the same master data, with the result written to the document immediately.

There is no API call to an external system. There is no post-processing reconciliation. There is no manual review step for standard transactions. The compliance result is the transaction result — correct by design, not by correction.

Why SAP Is the Right Layer

For multinationals running SAP, compliance-at-source means embedding the tax engine inside SAP itself — not sitting alongside it. Taxmarc is built in native SAP ABAP, which means it executes within the same process as every SD, MM, and FI document. It reads the same master data (material, customer, vendor, plant, business partner) that SAP uses for every other determination, and writes the result to the standard SAP tax fields that drive posting, reporting, and clearing.

This matters for three reasons. First, it means there is no latency or connectivity risk — the determination cannot fail because an external service is unavailable. Second, it means master data is never duplicated or out of sync between the ERP and a separate tax system. Third, it means the determination is fully auditable within the SAP document — tax authorities can be shown exactly which rule applied to which document and why.

Compliance-at-Source vs. Tax Engine APIs

Many organisations implement a tax engine as an external service called via API from SAP. This is a significant improvement over manual processes, but it falls short of true compliance-at-source. API-based architectures introduce latency, require synchronisation of master data between SAP and the external system, depend on network availability, and create a separation in the audit trail. When something goes wrong, it is not always clear whether the error originated in SAP, in the API call, or in the external engine.

Compliance-at-source eliminates these failure modes by collapsing the architecture. One system. One source of truth. One audit trail.

Regulatory and Audit Implications

Tax authorities across the EU — and increasingly in APAC and the Americas — are moving toward real-time or near-real-time reporting. Italy's SdI, Spain's SII, France's forthcoming e-invoicing mandate, and Germany's proposed CTC regime all require that tax determination is correct at the point of invoice creation, not corrected afterward. Compliance-at-source is not just good practice for these regimes — it is the only architecture that reliably meets them.

Implementing Compliance-at-Source in SAP

Implementing compliance-at-source requires a tax engine that is genuinely native to SAP — not a bolt-on connector that mimics integration. The engine must handle all transaction types (outbound sales, inbound procurement, intercompany, fixed assets, project systems), all document types, and all relevant country rules from a single configuration framework. Regulatory changes must be deployed as configuration updates, not as IT projects requiring ABAP development and transport cycles.

Taxmarc's platform is built on this model. Configuration covers 80+ countries, regulatory updates are deployed by the Taxmarc tax team without client IT involvement, and every determination is written to the SAP document with a full justification record accessible to tax and audit teams.