After the adoption of the Civil Law No. 743, the right ownership of the assets of the emerging foundations established as fused or annexed foundations was preserved subject to certain conditions both with the abolished Foundations Law No. 2762 and the Foundations Law No. 5737. In this context, the right to the surplus of income, which represents the amount remaining after the repair of the charity and the akars of the foundation and the performance of the charity services in the foundations, is protected in fused and annexed foundations. Regarding the income surplus, detailed regulations are included in the Foundations Regulation. According to the aforementioned regulations, a person must have a court decision showing that he or she is entitled to receive a surplus of income. It should be noted that in order for a person to take such a court decision, there must be a condition of excess income in the charter, and it must be proven that he or she is descended from the endowment. Another condition for being entitled to receive an income surplus is that the amount to be paid as an income surplus remains after deducting some expenses as per the Law. In the study, the concepts of foundation and income receivables within the scope of entitlement to the excess of income in old foundations will be emphasized, and examinations will be made on the case of determination of the fact that he or she is a foundation child.