IAS 8 and the global minimum tax: how an accounting adjustment can affect the 15%
By: Rebeca Sequeira
Financial Analyst | EAS LATAM
IAS 8 establishes how to select accounting policies, treat changes in estimates, and correct errors, while the global minimum tax of 15% seeks to ensure minimum taxation for large multinational groups, generally with consolidated revenues exceeding EUR 750 million. Both issues are closely related: the tax calculation is based on financial information, so an accounting classification at the local level can distort the effective rate reported at the group level.
In July 2026, the OECD preliminarily noted that multinationals subject to this tax had higher effective rates, without observing statistically significant reductions in investment or employment during the first year.
Why accounting does matter to the 15%
The 15% global minimum tax is based on financial information, but requires adjustments and a jurisdiction-specific calculation according to the GloBE Pillar Two rules. If the resulting effective tax rate (ETR) is less than 15%, a top-up tax may be levied. Therefore, proper accounting and tax reconciliations are essential for accurately determining this tax.
Local financial information has an impact on the group's tax calculations.
NIC 8: Three things you shouldn't mix
Prior period error: This occurs when reliable information that was already available was omitted or used incorrectly. It typically requires retrospective correction.
Change in accounting policy: Modifies recognition principles or bases. As a general rule, it is applied retrospectively, except in cases where the standard provides otherwise.
Change in accounting estimate: Responds to new information or changes in circumstances. Its effect is recognized exclusively going forward (prospective).
Impact of accounting correction on GloBE calculation
The GloBE rules do not simply apply a 15% rate to each entity's accounting profit. They start with the financial result, incorporate specific adjustments, and group the information by jurisdiction to calculate an effective rate. Therefore, any adjustment that modifies profit, opening equity, or taxes covered will alter the final result.
GloBE rules require reviewing prior period errors and changes in accounting principles to prevent income or expenses from being omitted from calculations or double-counted. In contrast, changes in estimates are typically recognized going forward.
This can directly affect the effective rate:
Case study: If an adjustment increases global income from US$10 million to US$11 million, while maintaining US$1.4 million in covered taxes, the effective tax rate falls from 14.0% to 12.7%. This widens the gap with the global minimum of 15%, resulting in a higher additional tax liability. Situations like this often arise in the treatment of long-term leases (IFRS 16).
What a subsidiary in Costa Rica should review
The global minimum tax threshold is determined at the level of the multinational group's parent company (consolidated revenues of at least EUR 750 million). Therefore, a small Costa Rican subsidiary is subject to these requirements if its group exceeds that limit.
Although this does not automatically imply paying a 15% tax at the local level, the subsidiary will be required to provide detailed financial and tax information to the parent company.
To reduce risks, the following is recommended:
Correctly classify accounting adjustments.
Identify the period of origin of the adjustment.
Reconcile taxes.
Report any corrections promptly.
A clear example of the gap between accounting recognition under IFRS and Costa Rican tax treatment is the treatment of exchange rate differentials .
Preventive review improves the traceability of the report.
Preliminary evidence published by the OECD in July suggests that the global minimum tax is already beginning to be reflected in the effective tax rates of the affected groups. For financial teams The 15% is not an isolated calculation that is reviewed after closing: a local figure can affect the jurisdictional result and the traceability of the report.
Prevention is the best strategy: consistent accounting policies, well-supported estimates, errors correctly identified under IAS 8 and early communication between Accounting, Tax and Consolidation.
Bibliographic references
· OECD. OECD publishes new analysis on the economic impacts of the Global Minimum Tax, July 15, 2026.