Article 72 establishes a strict symmetry between taxable income and deductible losses. It mandates that no loss may be deducted or carried forward if that loss was incurred while carrying on a business activity that was exempt from tax under either the Income Tax Law or any other Omani law. This prevents taxpayers from utilizing losses generated in tax-free sectors (such as certain industrial or agricultural exemptions) to offset profits earned in taxable sectors, ensuring that the benefit of an exemption does not extend to reducing the tax due on other activities.