Article 27 describes the process for assessing the Tax Due. While the Filing Constituent Entity initially self-assesses the tax according to Article 9, the National Bureau for Revenue retains the power to reassess the amount if errors are found in a return. Pursuant to Paragraph D, the Bureau may adjust an assessment if new facts or circumstances emerge that were previously unavailable. Furthermore, if a return is not submitted or if information is inadequate, the Bureau can independently assess the tax. These powers are subject to the procedural rules and controls specified in the Executive Regulations and Article 20.