The Bureau Of Internal Revenue (BIR) recently issued REVENUE MEMORANDUM ORDER NO. 40-2019. The said RMO has established the procedures for the proper service of assessment the BIR Notices in Accordance with the Provisions of Section 3.1.6 RR 18-2013.
The main objective of the RMO is to prescribe the proper procedures to be observed when serving the assessment notices such as Preliminary Assessment Notice (PAN), Final Assessment Notice (FAN)/Formal Letter of Demand (FLD) and Final Decision on Disputed Assessment (FDDA).

For the taxpayer, you have been served the right way if —
- It was personally delivered to you and to your registered business address;
- Substituted service; and
- Service by mail.
Substituted service is pretty much interesting mainly because it includes place of residence and disinterested party. Further, Barangay was given a specific role on the said RMO.
To know more about substituted service and service by mail, you can read the full RMO here.