Res Judicata
RES JUDICATA- the Latin term for "a matter [already] judged", and may refer to two things: in both civil law and common law legal systems, a case in which there has been a final judgment and is no longer subject to appeal.[1]; and the term is also used to refer to the legal doctrine meant to bar (or preclude) continued litigation of such cases between the same parties, which is different between the two legal systems. In this latter usage, the term is synonymous with"preclusion".

Elements of Res Judicata 1. The former judgment must be final 2. Judgment must be on the merits of the case 3. The former decision is rendered by the court having jurisdiction over the subject. 4. There is similar identity of parties, subject matter and cause of action for both cases.
Cause of action - defined as "an act or omission of second party in violation of the legal right or rights of the other, and its essential elements are legal right of the plaintiff, correlative obligation of the defendant, and act or omission of the defendant in violation of said legal right."

TEST FOR APPLICATION OF RES JUDICATA

In the application of the doctrine of res judicata, if it is doubtful whether a second action is for the same cause of action as the first, the test generally applied is to consider the Identity of facts essential to their maintenance, or whether the same evidence would sustain both. If the same facts or evidence would sustain both, the two actions are considered the same within the rule that the judgment in the former is a bar to the subsequent action. If, however, the two actions rest upon different states of facts, or if different proofs would be required to sustain the two actions, a judgment in one is no bar to the maintenance of the other.
LITIS PENDENTIALitis pendentia:

"a pending suit." same parties, same cause. Interposed as a ground for the dismissal of a civil action pending in court.Litis pendentia as a ground for the dismissal of a civil action refers to that situation wherein another action is pending between the same parties for the same cause of action, such that the second action becomes unnecessary and vexatious
Requisites for litis pendentia:(a) identity of parties or at least such as representing the same interests in both actions(b) identity of rights asserted and reliefs prayed for, the relief being founded on the same facts(c) the identity in the two cases should be such that the judgment that may be rendered in one would, regardless of which party is successful, amounts to res adjudicata in the other.Forum shopping à exists where the elements of litis pendentia are present, or where a final judgment in one case will amount to res judicata in the final other.Doctrine of Estoppel à an unlicensed foreign corporation doing business in thePhilippines may bring suit in Philippine courts against a Philippine citizen or entity who had contracted with and benefited from said corporation. A party is estopped from challenging the personality of a corporation after having acknowledged the same by entering into a contract with it. This doctrine of estoppel to deny corporate existence and capacity applies to foreign as well as domestic corporations.45 The application of this principle prevents a person contracting with a foreign corporation from later taking advantage of its noncompliance with the statutes chiefly in cases where such person has received the benefits of the contract.