The Pillar Two GloBE Information Return is a tax filing. Like any tax filing, it is subject to review, query and potential audit by tax authorities. Unlike most tax filings, the GIR covers ~480 data points per jurisdiction, draws from multiple source documents, and applies a layered computation that most tax authority staff will not be familiar with in year one. The audit trail requirements are correspondingly demanding.
What "traceable to source" actually means
Art. 7.2 of the Model Rules requires that information used in GloBE computations be drawn from the financial accounts used for consolidated reporting, or from separate financial statements — and that the source be documented. In practice, "traceable to source" means being able to demonstrate, for any GIR figure, the chain of steps from that figure back to a specific row in a specific source document, with the OECD rule applied at each step.
For a jurisdictional top-up tax figure of, say, €947,600, the chain looks like: top-up tax → top-up percentage × excess profit → max(0, 15% − GloBE ETR) and (GloBE Income − SBIE) → adjusted covered taxes ÷ GloBE Income and payroll + asset carve-out → current tax + deferred tax recast and trial balance rows → source document, row reference, column mapping. That is six or seven hops, each with a rule citation.
Why bolt-on audit trails fail
Some tools compute first and then reconstruct the trace as a separate step. This approach has a fundamental flaw: if the computation and the reconstruction run on different code paths — or if the inputs change between runs — the trace will not accurately reflect the computation. An auditor who tests the trace against the source data will find inconsistencies.
A defensible audit trail can only be generated as a by-product of computation itself. The provenance graph must be emitted at the point of calculation, not reconstructed afterwards.
Tamper-evidence
Beyond traceability, a strong audit trail is tamper-evident — the same inputs always produce the same outputs. This is achieved through cryptographic digests on every provenance node. If a single source figure is changed, the digest of every downstream node changes. An auditor can verify that the computation has not been altered after the fact by re-running the digest check.
What to retain and for how long
Most jurisdictions that have enacted GloBE rules require retention of records supporting the GIR for at least five to seven years from the filing date, consistent with general tax documentation rules. The records to retain include: source financial statements, all working papers, the full GIR (including any superseded versions), and the provenance trail linking GIR figures to source inputs. OECD guidance also recommends retaining the computation model — meaning the calculation engine or workbook — not just the outputs.
Pillar2OS generates a tamper-evident provenance trace on every computation and exports it as a PDF audit report, alongside the GIR XML. Start free.