Article 17 of the KSA Income Tax Law permits a depreciation deduction for tangible and intangible assets, excluding land, that lose value and are used to generate taxable income. Assets are classified into groups with specific annual depreciation rates: stationary buildings (5%), movable buildings (10%), factories and machinery (25%), geological exploration expenses (20%), and other assets like goodwill (10%). The deduction is calculated against the group's closing balance, which is adjusted by adding 50% of new asset costs and subtracting 50% of disposal proceeds. Special rules apply for low balances, complete group disposals, and assets under BOT/BOOT contracts.