Cabinet Decision No. 39 of 2019, Article 10, regulates interest deductions on loans from related parties. It introduces a thin capitalization rule, limiting deductible interest to loans not exceeding three times the company's equity. The loan must contribute to the taxpayer's economic benefit and be supported by a formal agreement. Crucially, interest paid by a sole proprietorship to its owner is strictly non-deductible. These measures are designed to prevent tax base erosion through excessive interest payments to associated entities or internal owners within the State of Qatar.