Any taxpayer may apply in writing, stating the basis therefor, to the Director for a revision of the tax assessed against him. Any request for a revision must be made within fifteen (15) days of the date on which the Director notifies the taxpayer of tax due pursuant to this Subdivision. If no application for revision is made within the fifteen (15) day period, the assessment is final. No application for revision shall be considered by the Director unless made within that period. The Director shall act upon such application promptly and shall provide notice to the taxpayer of the action.