The Court held that the sending of a PAN is part and parcel of the due process requirement in the issuance of a deficiency tax assessment and the BIR must strictly comply with the requirements laid down by the law and by its own rules. The importance of the PAN stage of the assessment process cannot be discounted as it presents an opportunity for both the taxpayer and the BIR to settle the case at the earliest possible time without need for the issuance of a FAN. (Prime Steel Mill, Inc. vs. Commissioner Of Internal Revenue, G.R. No. 249153, September 12, 2022)