In the Philippine legal system, marriage is considered an inviolable social institution. Consequently, the state protects the stability of marriage, and dissolving a union is a complex, strictly regulated process. It is important to distinguish between Annulment (rendering a valid marriage voidable) and a Declaration of Absolute Nullity (recognizing that the marriage was void from the beginning).

The primary governing law is Executive Order No. 209, otherwise known as the Family Code of the Philippines.

1. Void vs. Voidable Marriages

The legal grounds for ending a marriage depend on whether the marriage is classified as "Void" or "Voidable."

A. Declaration of Absolute Nullity (Void Marriages)

A void marriage is considered non-existent from the start (void ab initio). Under Articles 35, 37, and 38 of the Family Code, grounds include:

Lack of Essential Requisites: Marriages contracted without a valid marriage license or by an officer without authority.
Bigamous or Polygamous Marriages: Marriages contracted during the subsistence of a prior valid marriage.
Mistake in Identity: If one party married the wrong person by mistake.
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 step-parents and step-children.

B. Annulment (Voidable Marriages)

Under Article 45, a marriage is valid until it is set aside by a court decree. The grounds must exist at the time of the celebration of the marriage:

Lack of Parental Consent: If a party was between 18 and 21 and married without the consent of parents or guardians (unless they freely cohabited after reaching 21).
Insanity: If either party was of unsound mind at the time of marriage.
Fraud: Obtaining consent through deceptive means (e.g., concealment of a prior conviction, pregnancy by another man, or an STD).
Force, Intimidation, or Undue Influence: Consent obtained through threats or violence.
Physical Incapacity: If either party is permanently impotent and it was unknown to the other.
Serious and Incurable STD: If either party has a sexually transmitted disease found to be serious and incurable.

2. Psychological Incapacity (Article 36)

The most frequently cited ground in the Philippines is Article 36, which states:

"A marriage contracted by any party who, at the time of the celebration, was psychologically incapacitated to comply with the essential marital obligations of marriage, shall likewise be void..."

Following the landmark Supreme Court ruling in Tan-Andal vs. Andal (2021), the interpretation of psychological incapacity was refined:

Legal, not Medical: It no longer requires a clinical diagnosis by a psychologist or psychiatrist.
Gravity: The incapacity must be serious enough that the party cannot function as a spouse.
Juridical Antecedence: The incapacity must have existed at the time the marriage was celebrated, even if it manifested later.
Incurability: It must be incurable in a legal sense, meaning the spouse's personality structure makes them incapable of fulfilling marital vows.

3. Procedural Requirements for Filing

Filing for a decree of nullity or annulment involves a rigorous judicial process.

Step 1: The Petition

The petitioner must file a verified petition in the Family Court of the province or city where the petitioner or the respondent has been residing for at least six months.

Step 2: Summons and Answer

The court issues a summons to the respondent, who has 15 to 30 days to file an answer. If no answer is filed, the court cannot automatically grant the petition; it must ensure no collusion exists.

Step 3: Investigation of Collusion

The Public Prosecutor (Fiscal) is mandated to conduct an investigation to determine if the parties have "cooked up" the case or agreed to the annulment. The state’s role is to defend the sanctity of marriage.

Step 4: Pre-Trial and Trial

Evidence is presented, including testimony from the petitioner, witnesses, and often psychological experts. The Office of the Solicitor General (OSG) may intervene to oppose the petition if it deems the grounds insufficient.

4. Effects of the Decree

Once the court issues a Final Decree of Annulment or Nullity, several legal consequences follow:

Category	Legal Effect
Marital Status	The parties are restored to the status of "single" and can legally remarry.
Property Relations	The absolute community or conjugal partnership is dissolved. Properties are liquidated and partitioned.
Children's Status	Children of voidable marriages or Article 36 marriages are generally considered legitimate.
Custody & Support	The court will decide on child custody and support based on the "Best Interest of the Child" principle.

5. Mandatory Documentary Requirements

To initiate the process, the following documents are typically required:

PSA Marriage Certificate (Original copy).
PSA Birth Certificates of the children (if any).
Barangay Certificate or proof of residency of the petitioner.
Psychological Evaluation Report (While not strictly required per Tan-Andal, it remains the strongest form of evidence).
Inventory of Assets (If property partition is involved).