ISSUE: Whether or not COA is allowed to conduct post-audit.
FACTS: DBP conducted a public bidding for one unit of uninterruptible power supply (UPS). Thereafter, DBP issued Purchase Order No. 0137 to Voltronics for P1,436,539.25 inclusive of customs duties and taxes. COA sent a notice to the chairman of DBP notifying him of the disallowance of the amount representing customs duties and taxes and at the same time holding him, along with other petitioners, jointly and severally liable for the aforementioned sum. They submit the contrary on the ground that the transaction in question had already been approved and passed in audit in accordance with the pre-audit system then obtaining and the later circular requiring post-audit should not be applied retroactively
DECISION: Yes. COA can conduct post-audit.
RATIO DECIDENDI: While it is true that the applicable procedure in force at the time of the questioned transaction was COA Circular 86-257 requiring a pre-audit, there is nothing to preclude COA from conducting a post-audit of the already pre-audited transaction. Article IX (D) Section 2(1) of the Constitution expressly grants respondent Commission the power to conduct a post-audit.