A basic tenet in our rules of procedure is that an award that is final and executory cannot be amended or modified anymore. Nothing is more settled in law than that once a judgment attains finality it thereby becomes immutable and unalterable. It may no longer be modified in any respect, even if the modification is meant to correct what is perceived to be an erroneous conclusion of fact or law, and regardless of whether the modification is attempted to be made by the court rendering it or by the highest court of the land. However, this rule is subject to exceptions as stated in the case of David vs. CA, 316 SCRA 710 (1999), cited by respondent:
One exception is that where facts and/or events transpire after a decision has become executory, which facts and/or events present a supervening cause or reason which renders the final and executory decision no longer enforceable. Under the law, the court may modify or alter a judgment even after the same has become executory whenever circumstances transpire rendering its execution unjust and inequitable, as where certain facts and circumstances justifying or requiring such modification or alteration transpired after the judgment has become final and executory.
In David, we held also that “where an execution order [which] has been issued is still pending, all proceedings on the execution are still proceedings in the suit.” As such, modification of the execution of such judgment is allowed.
In Torres vs. National Labor Relations Commission, 330 SCRA 311 (2000), this Court ruled that:
Execution is the final stage of litigation, the end of the suit. It cannot be frustrated except for serious reasons demanded by justice and equity. In this jurisdiction, the rule is that when a judgment becomes final and executory, it is the ministerial duty of the court to issue a writ of execution to enforce the judgment. A writ of execution may however be refused on equitable grounds as when there was a change in the situation of the parties that would make execution inequitable or when certain circumstances, which transpired after judgment became final, rendered execution of judgment unjust. The fact that the decision has become final does not preclude a modification or an alteration thereof because even with the finality of judgment, when its execution becomes impossible or unjust, it may be modified or altered to harmonize the same with justice and the facts (emphasis supplied). 
In Deltaventures Resources Inc. vs. Cabato, 327 SCRA 521 (2000), we held that “jurisdiction once acquired is not lost upon the instance of the parties but continues until the case is terminated.” The power of a voluntary arbitrator to issue a writ of execution carries with it the power to inquire into the correctness of its execution and to consider whatever supervening events transpire during execution. Therefore, we are in agreement with the appellate court that a voluntary arbitrator has jurisdiction to amend the mode of executing an award if and when the case merits such amendment.