Article 28 of the KSA Income Tax Law establishes the principle for the tax treatment of income and expenses derived from jointly-owned property. It mandates that any such income or related expenses must be apportioned among the partners or co-owners. The basis for this allocation is strictly defined as the proportion of each partner's respective share in the property. This ensures a fair and equitable distribution of tax liabilities and deductions, directly linking the financial consequences to the ownership percentage of each individual involved in the joint venture or co-ownership arrangement.