Article 151 addresses the payment of additional taxes found after an official audit. If the Tax Authority's assessment determines a higher tax liability than what was originally declared and paid with the return, the excess amount becomes due. This additional tax must be paid by the specific date mentioned in the assessment notice (per Article 146). This provision ensures that any discrepancies found during the Authority's review process are promptly settled, bridging the gap between the taxpayer's self-assessment and the state's official determination of the correct tax liability.