Article 170 bis mandates the final administrative step following a grievance outcome. Once the Committee issues its decision, the Tax Authority is legally required to make the 'necessary assessment' to give effect to that decision. This ensures that the Authority's financial records for the taxpayer are updated to match the Committee's ruling (e.g., reducing the tax bill if the grievance was successful). This provision ensures that the Committee's independent findings are practically implemented into the taxpayer's official assessment status and collection records.