Short answer. No. Annulment, nullity, and legal separation cases are excluded from the default rule. If you don't answer, the court cannot simply grant the petition; it must direct the public prosecutor or the Solicitor General's deputy to investigate whether you and your spouse are colluding, and to make sure the evidence presented is genuine.
What the law says
If the defending party in action for annulment or declaration of nullity of marriage or for legal separation fails to answer, the court shall order the Solicitor General or his or her deputized public prosecutor, to investigate whether or not a collusion between the parties exists, and if there is no collusion, to intervene for the State in order to see to it that the evidence submitted is not fabricated.
Rule 9, Section 3 — Default; [d]eclaration of. Read the full provision →
Why default judgments don't apply here
The general rule under the Rules of Court is that a defending party who fails to answer within the time allowed can be declared in default, after which the court may render judgment granting whatever relief the other side's pleading asks for. Rule 9, Section 3 carves out an exception for certain family cases: it expressly states that no default is allowed in an action for annulment or declaration of nullity of marriage or for legal separation. This exception exists because these cases involve the marriage bond itself, not just a private dispute between two parties, so the outcome is not left to turn on whether one spouse simply stayed silent.
What happens instead: the collusion investigation
Instead of a default order, the rule directs the court to bring in a public authority. If the defending spouse fails to answer, the court must order the Solicitor General, or a public prosecutor deputized for the purpose, to investigate whether the two spouses are colluding to obtain the annulment, nullity, or legal separation. Collusion means the parties have arranged between themselves to fabricate or manufacture a ground, or to simply let the case go unopposed, so that the marriage is dissolved without a genuine dispute being tried. The point of the inquiry is to protect the integrity of the proceeding itself, not to punish the spouse who failed to respond.
What the prosecutor is checking for
If the investigation finds no collusion, the prosecutor's role does not end there. The rule requires the prosecutor to intervene for the State to make sure that whatever evidence the petitioning spouse submits is not fabricated. In practice this means the case still has to be proven on real evidence, tested in some fashion, before the court can rule, even though the other spouse never filed an answer. A silent or absent spouse does not automatically hand the petitioner a win; the State stands in to see that the ground alleged is genuinely established.
What silence does not do
Because a default order is unavailable in these actions, staying silent does not forfeit your right to appear later and contest the case, the way it might in an ordinary civil suit. It does mean, however, that the case can and typically will proceed, since the absence of an answer does not stop the court from moving forward once the collusion investigation is addressed. If you were served with a petition for annulment, nullity, or legal separation and have not yet answered, the safer course is to find out where the case stands rather than assume nothing can happen until you respond.