How Is the Effective Tax Rate (ETR) Calculated? A Step-by-Step Example
Pillar 2 revolves around a single rate. That rate is derived not from the tax base you're used to, but from your financial statements — and that difference changes everything.
Why Does It Matter?
If the effective tax rate is below 15%, a top-up tax arises; if it is above, it does not. Getting this calculation wrong means you either pay unnecessary tax or face a penalized reassessment years later.
The Formula
ETR = Adjusted Covered Taxes ÷ Net GloBE Income
The calculation is performed on a jurisdictional basis, not a company basis. The figures for all your group companies in Türkiye are combined into a single Turkish rate. A profitable company and a loss-making company are melted into the same pot.
Step by Step
Step 1 — Determine net GloBE income. The starting point is the accounting profit under the financial statements used for consolidation — not the tax base. This amount is adjusted for items set out in the legislation (such as dividend exemptions, certain non-deductible expenses, and prior-period errors).
Step 2 — Determine covered taxes. Corporate tax and similar taxes are taken into account. Deferred tax effects are also factored in under specific rules. Taxes not levied on income, such as VAT or stamp duty, are excluded from this amount.
Step 3 — Find the rate and the shortfall. Top-up tax rate = 15% − ETR.
Step 4 — Determine the tax base. The shortfall rate is applied not to the entirety of net GloBE income, but to the amount remaining after the substance-based income exclusion is deducted. This exclusion carves out a set percentage of payroll costs and tangible assets in the jurisdiction from the calculation. It exists to protect companies with genuine production and employment; the percentages start higher during the transition period and gradually decline to 5%.
Areas of Legal Interpretation in the Calculation
Not every adjustment made in moving from financial accounting net income or loss to GloBE income is of the same nature. Special rules apply to dividends and equity gains, asymmetric foreign exchange differences, intra-group financing transactions, share-based payments, pension obligations, and prior-period errors. Which item is adjusted matters as much as which entity and jurisdiction the adjustment is allocated to — both affect the outcome.
The deferred tax mechanism is particularly important. To prevent temporary differences from artificially lowering the effective tax rate, the system takes deferred tax expense into account within certain limits; however, where certain deferred tax liabilities fail to reverse within a specified period, prior calculations may need to be revisited. For this reason, a preliminary calculation based solely on the current tax provision may not reflect the true liability. To make the calculation defensible later, the data dictionary, the accounting standard used, the rationale for adjustments, currency translations, and elections made should all be documented in writing.
A Simple Example
The combined figures of your group companies in Türkiye:
In this simplified example, although the statutory rate in Türkiye is 25%, the Pillar 2 effective tax rate falls to 11%, and after the substance-based income exclusion, a top-up tax of TRY 12 million arises. In an actual calculation, the domestic top-up tax, safe harbours, prior-period adjustments, and other special rules may change the outcome.
Points to Note
"Since we already pay the domestic minimum corporate tax, Pillar 2 isn't a concern for us."
These are two separate taxes, and confusing them is very common. The domestic minimum corporate tax (Corporate Tax Law Art. 32/C) is a domestic safeguard applied to all corporate taxpayers, calculated on a percentage of corporate income before deductions and exemptions. The domestic minimum top-up corporate tax, on the other hand, is part of Pillar 2 — it applies only to multinational groups exceeding the €750 million threshold and is calculated on an entirely different GloBE-based tax base. Amounts paid under the domestic minimum corporate tax may, depending on their nature, affect the covered-taxes calculation, but they do not automatically eliminate the Pillar 2 liability.
Action Items
- Have your ETR calculation performed jointly with your financial advisor, on a jurisdictional basis
- Ensure your deferred tax items are correctly classified
- Keep your payroll and tangible-asset data ready for the substance-based income exclusion
- Document in writing the assumptions, data dictionary, and rationale for adjustments underlying the calculation — these documents will form your defense if a dispute arises
Conclusion
Tax and finance teams play a central role in preparing the calculation. That said, scope, data quality, elections, filing responsibility, and the defensibility of contentious interpretations additionally require legal assessment.