• This case clarifies the evidentiary requirement for proving service by registered mail in administrative proceedings. A municipal officer, Victoria Labastida, had her appeal to the Civil Service Commission (CSC) dismissed for being filed late, a decision affirmed by the Court of Appeals (CA). Both bodies relied on a registry return receipt marked "refused to accept" as conclusive proof of service. The Supreme Court reversed this, ruling that a registry return receipt alone is insufficient. It must be accompanied by an affidavit from the postmaster. Given the lack of proper proof and other contradictory evidence, the Court held that the appeal was timely filed and remanded the case to the CSC for a decision on the merits.

• The Complaint: Monina Quires filed an administrative complaint against Victoria Labastida, a Municipal Planning and Development Officer, for gross neglect of duty and conduct prejudicial to the best interest of the service.
• The Dismissal: On June 10, 2016, the Municipal Mayor found Labastida guilty and dismissed her from service. A copy of this decision was supposedly sent to her via registered mail.
• Disputed Service: The registry return receipt for the decision was annotated "refused to accept 06-14-16" and signed by an unidentified person. Labastida denied ever receiving it or refusing it.
• Actual Notice and Appeal: Labastida claimed she only learned of the decision on March 8, 2017, through a Notice of Suspension from the Commission on Audit (COA). She then filed her appeal with the CSC on March 16, 2017.

• CSC Ruling: The CSC dismissed the appeal for being filed out of time. It relied on the registry return receipt and the presumption of regularity, considering the decision served on June 14, 2016.
• Court of Appeals (CA) Ruling: The CA affirmed the CSC's dismissal on the same grounds.

• Is a registry return receipt alone sufficient to prove service by registered mail, especially when receipt is denied?
• When should the 15-day period to appeal to the CSC be reckoned?

The Supreme Court GRANTED the petition, REVERSING the CA and CSC, and REMANDED the case to the CSC for a decision on the merits.

• Insufficient Proof of Service: The registry return receipt alone is not sufficient proof of service. Under the Rules of Court, it must be accompanied by an affidavit from the postmaster or the person mailing it. The disputable presumption of regularity was overcome by Labastida's denial and the corroborating evidence (no record of the case in the Mayor's office, unidentified signature on the receipt).
• Appeal was Timely Filed: Since there was no valid proof of service on June 14, 2016, the 15-day appeal period should be reckoned from March 8, 2017, the date Labastida actually received the decision. Therefore, her appeal filed on March 16, 2017 was filed on time.
• Substantial Justice over Technicalities: The Court emphasized that in exceptional cases, strict procedural rules must yield to the requirements of due process and substantial justice, especially when a person's constitutional right to security of tenure is at stake.

• Proof of Service by Registered Mail: Under the Rules of Court, proof of service by registered mail requires both the registry return receipt and an affidavit from the mailer or a certification from the postmaster. The receipt alone is not sufficient.
• Disputable Presumptions: The presumptions of regularity in the performance of official duty and receipt of mailed letters are *disputable*. They can be overcome by a direct denial coupled with clear and convincing contrary evidence.
• Liberal Construction of Rules: Procedural rules should not be applied so rigidly as to defeat substantial justice, especially in administrative cases where a party's constitutional rights (like security of tenure) are at stake.