In the Philippines, marriage is legally protected as an "inviolable social institution." Unlike many other jurisdictions, the country does not have a system for absolute divorce (except for Muslim Filipinos under the Code of Muslim Personal Laws). Instead, the legal remedies available to end a marriage involve either Declaration of Absolute Nullity or Annulment.

While often used interchangeably in casual conversation, they are distinct legal concepts under the Family Code of the Philippines.

1. Nullity vs. Annulment: The Fundamental Difference

Declaration of Absolute Nullity (Void Marriages): This applies to marriages that are considered void from the beginning (void ab initio). In the eyes of the law, the marriage never existed.
Annulment (Voidable Marriages): This applies to marriages that are considered valid until they are set aside by a court decree. These marriages have a "defect" at the time of celebration that allows one party to seek its termination.

2. Grounds for Declaration of Absolute Nullity (Void Marriages)

Under Articles 35, 36, 37, and 38 of the Family Code, a marriage is void if:

Lack of Legal Capacity: Either party is below 18 years of age, even with parental consent.
Lack of Authority: The solemnizing officer had no legal authority (unless either or both parties believed in good faith that the officer had such authority).
No License: The marriage was performed without a valid marriage license (except in specific exempt cases like marriages in articulo mortis).
Bigamous or Polygamous Marriages: Marriages contracted during the subsistence of a prior marriage.
Mistake in Identity: One party married the other under a mistake as to the latter’s identity.
Psychological Incapacity (Article 36): This is the most common ground cited. It occurs when one or both parties are mentally or psychically incapable of complying with the essential marital obligations (e.g., procreation, mutual love, respect, and fidelity).
Incestuous Marriages: Between ascendants and descendants, or siblings (full or half-blood).
Public Policy Violations: Marriages between collateral blood relatives up to the fourth civil degree (first cousins) or between step-parents and step-children.

3. Grounds for Annulment (Voidable Marriages)

Under Article 45, a marriage may be annulled for the following reasons existing at the time of the marriage:

Lack of Parental Consent: If a party was between 18 and 21 and married without parental consent (unless they continued to live together freely after reaching 21).
Unsound Mind: Either party was incapable of giving intelligent consent.
Fraud: Consent was obtained through deceptive means (e.g., non-disclosure of a prior conviction, drug addiction, or pregnancy by another man).
Force, Intimidation, or Undue Influence: Consent was obtained through coercion.
Impotence: Physical inability to consummate the marriage, and such inability appears to be incurable.
Serious Sexually Transmitted Disease (STD): If the STD is found to be serious and appears to be incurable.

4. The Legal Procedure

The process is governed by the Rule on Declaration of Absolute Nullity of Void Marriages and Annulment of Voidable Marriages (A.M. No. 02-11-10-SC).

Step 1: Filing the Petition

The petition must be filed in the Family Court of the province or city where the petitioner or the respondent has been residing for at least six months prior to the date of filing.

Step 2: Summons and Answer

The court issues a summons to the respondent. The respondent has 15 days to file an answer. If no answer is filed, the court cannot simply declare a default judgment.

Step 3: Investigation by the Public Prosecutor

Because the State has an interest in protecting marriage, a Public Prosecutor is assigned to investigate whether collusion exists between the parties (i.e., if they are working together just to get the marriage ended quickly). If collusion is found, the case is dismissed.

Step 4: Pre-Trial Conference

The parties appear before the judge to simplify the issues, mark evidence, and stipulate facts. In the Philippines, the petitioner's presence is mandatory during pre-trial.

Step 5: Trial

The petitioner must present evidence and witnesses (such as psychologists or psychiatrists in Article 36 cases) to prove the grounds cited. The State, through the Solicitor General or Prosecutor, may cross-examine witnesses to ensure the integrity of the proceedings.

Step 6: Decision and Finality

If the court grants the petition, it issues a Decree of Nullity or Annulment. However, the decree is only issued after the liquidation of assets, partition of property, and determination of custody and support.

5. Effects of the Decree

Status: The parties are returned to the status of "single." They are legally free to remarry.
Property: The absolute community of property or conjugal partnership is dissolved.
Children:
- In void marriages under Article 36 (Psychological Incapacity) and Article 53, children are considered legitimate.
- In most other void marriages, children are considered illegitimate.
- In annulled (voidable) marriages, children conceived before the decree are legitimate.
Support and Custody: The court will decide on child support and custody based on the "best interests of the child" principle.