When a company’s allowable deductions exceed its gross taxable income, it incurs a tax loss. Tax laws allow companies to carry these losses forward to offset against future taxable profits, reducing their future tax burden. To protect public revenue, tax codes often limit this benefit by capping the carry-forward period (e.g., up to 10 consecutive years) or restricting the offset to profits generated within the same business line.

Multinational companies often try to shift profits out of high-tax countries by funding their local subsidiaries with large internal loans rather than equity. Because interest payments on debt are tax-deductible while dividend payouts are not, the subsidiary can use high interest payments to reduce its taxable profit to zero.

  [ Parent Company in Low-Tax Country ] ===== Issues High-Interest Loan =====> [ Local Subsidiary ]
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  [ Low Corporate Tax Paid ] <====== Reduces Taxable Profit via Interest Expense ==+

To combat this, tax authorities enforce Thin Capitalization Rules. These rules establish a maximum debt-to-equity ratio (e.g., 3:1). Any interest expense generated by debt that exceeds this limit is treated as a non-deductible disallowable expense.

Modern tax frameworks use an earnings-based approach aligned with the OECD BEPS framework. This method caps a company’s net interest deductions at a set percentage (e.g., 30%) of its Earnings Before Interest, Taxes, Depreciation, and Amortization (EBITDA), replacing historical debt-to-equity ratios with a dynamic economic limit.