Sep 21, 2026
By Rebeca Sequeira
Financial Analyst | EAS LATAM
IAS 8 establishes how to select accounting policies, account for changes in estimates, and correct errors. Meanwhile, the 15% global minimum tax seeks to ensure a minimum level of taxation for large multinational groups, generally those with consolidated revenue exceeding EUR 750 million. The two issues are closely connected: the tax calculation begins with financial information, meaning that a local accounting classification can distort the effective tax rate reported at the group level.
In July 2026, the OECD preliminarily reported that multinational enterprises subject to the tax had higher effective tax rates, with no statistically significant decline in investment or employment during the first year.
Why Accounting Matters for the 15% Rate
The 15% global minimum tax uses financial information as its starting point, but it requires adjustments and a jurisdiction-by-jurisdiction calculation under the Pillar Two GloBE rules. If the resulting effective tax rate (ETR) is below 15%, a top-up tax may arise. Accurate financial close procedures and tax reconciliations are therefore essential to determining the tax correctly.
Local financial information affects the group’s tax calculations.
IAS 8: Three Concepts That Should Not Be Confused
Prior-period error: This exists when reliable information that was already available was omitted or used incorrectly. As a general rule, it requires retrospective correction.
Change in accounting policy: This changes the principles or bases of recognition. As a general rule, it is applied retrospectively unless the standard provides an exception.
Change in accounting estimate: This results from new information or changes in circumstances. Its effect is recognized prospectively only.
How an Accounting Correction Affects the GloBE Calculation
The GloBE rules do not simply apply a 15% rate to each entity’s accounting income. They begin with financial accounting net income or loss, incorporate specific adjustments, and aggregate information by jurisdiction to calculate an effective tax rate. Any adjustment that changes income, opening equity, or covered taxes can therefore alter the final result.
The GloBE rules require a review of prior-period errors and changes in accounting principles to prevent income or expenses from being omitted from the calculation or counted twice. Changes in estimates, by contrast, are generally recognized prospectively.
This can directly affect the effective tax rate:
Practical example: If a correction increases GloBE income from US$10 million to US$11 million while covered taxes remain at US$1.4 million, the effective tax rate falls from 14.0% to 12.7%. This widens the gap below the 15% global minimum and results in a higher top-up tax. Situations like this often arise in the accounting for long-term leases under IFRS 16.
What a Costa Rican Subsidiary Should Review
The global minimum tax threshold is determined at the multinational group’s parent-company level—consolidated revenue of at least EUR 750 million. As a result, even a small Costa Rican subsidiary is subject to these requirements if its group exceeds that threshold.
Although this does not automatically mean paying a 15% tax locally, the subsidiary will be required to provide detailed financial and tax information to its parent company.
To reduce risk, companies should:
Classify accounting adjustments correctly.
Identify the period in which each adjustment originated.
Reconcile taxes.
Communicate corrections promptly.
Foreign-exchange differences provide a clear example of a gap between accounting recognition under IFRS and Costa Rican tax treatment.
A proactive review improves reporting traceability.
Preliminary evidence published by the OECD in July suggests that the global minimum tax is already beginning to appear in the effective tax rates of covered groups. For finance teams, the 15% rate is not a stand-alone calculation performed after the close: a local figure can affect both the jurisdictional result and the audit trail supporting the report.
Prevention is the best strategy: consistent accounting policies, well-supported estimates, errors properly identified under IAS 8, and early communication among Accounting, Tax, and Consolidation teams.
Bibliography
IFRS Foundation. IAS 8 – Basis of Preparation of Financial Statements.
OECD. OECD Publishes New Analysis on the Economic Impacts of the Global Minimum Tax, July 15, 2026.
Contreras, L., Hugger, F., and Zawisza, T. (2026). MNE Responses to the Global Minimum Tax. OECD Taxation Working Papers, No. 77.
OECD. Global Anti-Base Erosion Model Rules (Pillar Two) and 2026 Consolidated Commentary.