The Supreme Court has ruled that the Commissioner of Internal Revenue must personally serve taxpayers or their authorized representatives with both the notice of informal conference and the preliminary assessment notice before issuing a final assessment notice.

The ruling, issued by the Third Division in a case involving Mannasoft Technology Corporation, clarified the procedural requirements for tax assessments under Section 228 of the Tax Code and Revenue Regulations No. 12-99.

Mannasoft's case stemmed from a tax investigation for calendar year 2008. The CIR served the company with a NIC and a PAN through a "Client Service Assistant," not a duly authorized representative, prompting legal challenges.

The CIR later issued a FAN assessing substantial deficiency taxes based on the investigation. Mannasoft disputed the assessment and requested a reinvestigation, arguing that the initial notices were improperly served.