In every tax assessment, due process requires that the Bureau of Internal Revenue (BIR) properly apprise the taxpayer of the nature of the tax liability, the amount due, and the law and basis for such assessment.

To streamline due process requirements, the BIR issued Revenue Regulations (RR) 12-99 as amended by RRs 18-2013 and 7-2018, that requires the issuance of BIR notices - such as Notice of Informal Conference, Preliminary Assessment Notice, Final Assessment Notice (FAN) together with a Formal Letter of Demand (FLD) and a Final Decision on Disputed Assessment (FDDA) - to the taxpayer. Once the taxpayer receives the final decision and demands for payment, he/she can elevate the matter before the Court of Tax Appeals (CTA) within 30 days from receipt of the decision.