Article 159 bis 2 imposes a strict reporting duty on small enterprises. If an event occurs that causes the enterprise to no longer meet the eligibility conditions (e.g., an increase in capital, income, or employees beyond the limits), the enterprise must notify the Tax Authority within 15 days. This notification must be accompanied by official supporting documents. This ensures that the transition from a simplified small-business regime to the standard 15% tax regime happens promptly as the business grows, maintaining the fiscal integrity of the differentiated tax system.