Article 30 of the KSA Income Tax Law establishes the official currency for tax calculations. It mandates that a taxpayer's gross income and resulting tax base must be calculated and declared in Saudi Riyal (SAR). For any financial transactions or income amounts recorded in a currency other than the Saudi Riyal, a conversion is required for taxation purposes. The article specifies that the conversion must use the official exchange rate declared by the Saudi Arabian Monetary Agency (SAMA). The applicable rate is the one effective on the specific date the transaction occurred, ensuring consistency and accuracy in reporting.